Methods and apparatus to facilitate atomic compare and swap in cache for a coherent level 1 data cache system

ABSTRACT

Methods, apparatus, systems and articles of manufacture to facilitate atomic compare and swap in cache for a coherent level 1 data cache system are disclosed. An example system includes a cache storage; a cache controller coupled to the cache storage wherein the cache controller is operable to: receive a memory operation that specifies a key, a memory address, and a first set of data; retrieve a second set of data corresponding to the memory address; compare the second set of data to the key; based on the second set of data corresponding to the key, cause the first set of data to be stored at the memory address; and based on the second set of data not corresponding to the key, complete the memory operation without causing the first set of data to be stored at the memory address.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/882,272, filed on May 22, 2020, which claims the benefit of U.S.Provisional Patent Application No. 62/852,494, filed on May 24, 2019,each of which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to computer architecture, and, moreparticularly, to methods and apparatus to implement a data cache.

BACKGROUND

Computing systems include one or more processing cores to executeinstructions by accessing data stored in memory. However, the amount oftime it takes for the processing core to access data from the memory canbe significant. Accordingly, most computing systems include a cachewhich stores an amount of data from the memory (e.g., typically smallerthan the total amount of data in the memory) that has a high probabilityof being accessed by the processing core in the future. Accordingly,when the processing core calls for data, the cache can provide the datato the processing core faster than the processing core retrieving thedata from the memory, thereby increasing the speed and efficiency of thecomputing system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example computing system described in conjunction withexamples disclosed herein.

FIG. 2 is a block diagram of an example level one cache of the examplecomputing system of FIG. 1.

FIGS. 3A-3D illustrate an example circuit implementation of the levelone cache of the example computing system of FIG. 1.

FIG. 4A is an example circuit implementation of the main cache storequeue of FIGS. 3A-3D.

FIG. 4B is an example circuit implementation of example data forwardinglogic implemented in connection with the main cache store queue of FIGS.3A-4A.

FIG. 4C is an additional example circuit implementation of the maincache store queue and/or of a victim cache store queue.

FIG. 4D is an example hardware implementation of a merging circuit ofFIG. 4A.

FIG. 5 illustrates an example victim cache-based section of the levelone cache of FIGS. 3A-3D.

FIG. 6 illustrates an example first table and an example second tablefor implementing an example replacement policy component of FIGS. 3A-3Dand 5.

FIG. 7A illustrates an example encapsulated data cache system includinga victim cache store queue and victim storage.

FIG. 7B illustrates another example encapsulated data cache systemincluding a main cache store queue and main storage.

FIG. 7C illustrates an example victim cache bank structure.

FIG. 7D illustrates an example main cache bank structure.

FIG. 7E illustrates an example unified cache bank structure.

FIG. 8A illustrates a schematic illustration of an exampleimplementation of victim cache tag random access memory.

FIG. 8B illustrates another schematic illustration of the exampleimplementation of the victim cache tag random access memory of FIG. 8A.

FIGS. 9A and 9B (collectively FIG. 9) illustrate example instructionservicing workflows.

FIGS. 10A-1 and 10A-2 (collectively FIG. 10A) illustrate an example datacache system.

FIGS. 10B-1 and 10B-2 (collectively FIG. 10B) illustrate a secondexample data cache system.

FIG. 11A is an example circuit implementation of the victim cache storequeue of FIGS. 3A-3D.

FIGS. 11B-1 and 11B-2 (collectively FIG. 11B) illustrate an examplecircuit implementation of an example unified cache store queue.

FIG. 12-33 are flowcharts representative of machine readableinstructions which may be executed to implement the level one cache ofFIGS. 1-3D.

FIG. 34 is a block diagram of an example processing platform structuredto execute the instructions of FIGS. 3A-3D to implement the level onecache of FIGS. 1-3D.

DETAILED DESCRIPTION

The figures are not to scale. Instead, the thickness of the layers orregions may be enlarged in the drawings. In general, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts. As used in this patent,stating that any part (e.g., a layer, film, area, region, or plate) isin any way on (e.g., positioned on, located on, disposed on, or formedon, etc.) another part, indicates that the referenced part is either incontact with the other part, or that the referenced part is above theother part with one or more intermediate part(s) located therebetween.Connection references (e.g., attached, coupled, connected, and joined)are to be construed broadly and may include intermediate members betweena collection of elements and relative movement between elements unlessotherwise indicated. As such, connection references do not necessarilyinfer that two elements are directly connected and in fixed relation toeach other. Stating that any part is in “contact” with another partmeans that there is no intermediate part between the two parts. Althoughthe figures show layers and regions with clean lines and boundaries,some or all of these lines and/or boundaries may be idealized. Inreality, the boundaries and/or lines may be unobservable, blended,and/or irregular.

Various forms of the term “couple” are used throughout thespecification. These terms may cover connections, communications, orsignal paths that enable a functional relationship consistent with thedescription of the present disclosure. For example, if device Agenerates a signal to control device B to perform an action, in a firstexample device, A is coupled to device B by direct connection, or in asecond example device, A is coupled to device B through interveningcomponent C if intervening component C does not alter the functionalrelationship between device A and device B such that device B iscontrolled by device A via the control signal generated by device A.

Consistent with the present disclosure, the term “configured to”describes the structural and functional characteristics of one or moretangible non-transitory components. For example, a device that is“configured to” perform a function mean that the device has a particularconfiguration that is designed or dedicated for performing a certainfunction. A device is “configured to” perform a certain function if sucha device includes tangible non-transitory components that can beenabled, activated, or powered to perform that certain function. Whilethe term “configured to” may encompass being configurable, this term isnot limited to such a narrow definition. Thus, when used for describinga device, the term “configured to” does not require the described deviceto be configurable at any given point of time.

Moreover, the term “example” is used herein to mean serving as aninstance, illustration, etc., and not necessarily as advantageous. Also,although the disclosure has been shown and described with respect to oneor more implementations, equivalent alterations and modifications willbe apparent upon a reading and understanding of this specification andthe annexed drawings. All such modifications and alterations are fullysupported by the disclosure and is limited only by the scope of thefollowing claims. In particular regard to the various functionsperformed by the above described components (e.g., elements, resources,etc.), the terms used to describe such components are intended tocorrespond, unless otherwise indicated, to any component which performsthe specified function of the described component (e.g., that isfunctionally equivalent), even though not structurally equivalent to thedisclosed structure. In addition, while a particular feature of thedisclosure may have been disclosed with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular application.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features that may be specific to particularembodiments. Certain features that are described in this specificationin the context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in an exampleparticular order, this does not require that such operations beperformed in the example particular order shown or in sequential order,or that all illustrated operations be performed, to achieve desirableresults unless such order is recited in one or more claims. In certaincircumstances, multitasking and parallel processing may be advantageous.Moreover, the separation of various system components in the embodimentsdescribed above does not require such separation in all embodiments.

Descriptors “first,” “second,” “third,” etc. are used herein whenidentifying multiple elements or components which may be referred toseparately. Unless otherwise specified or understood based on theircontext of use, such descriptors do not impute any meaning of priority,physical order or arrangement in a list, or ordering in time but aremerely used as labels for referring to multiple elements or componentsseparately for ease of understanding the disclosed examples. In someexamples, the descriptor “first” may be used to refer to an element inthe detailed description, while the same element may be referred to in aclaim with a different descriptor such as “second” or “third.” In suchinstances, it should be understood that such descriptors are used merelyfor ease of referencing multiple elements or components.

A central processing unit (CPU) is electronic circuitry that executesinstructions making up a program or workload. A CPU may include one ormore processor cores to execute the instructions by accessing data frommain memory (e.g., extended memory). Because it takes time to accessdata from main memory, the one or more processor cores may obtain datafrom the memory and store it locally in local memory (e.g., a datacache). The local memory is smaller and faster than the main memory. Inthis manner, the processor cores can use and/or manipulate the datalocally rather than interfacing with the main memory. Because thelatency (e.g., the amount of time needed to read and/or write datato/from memory) for reading and/or righting data is smaller whenaccessing the cache, storing data from the extended memory in the cacheincreases the speed and efficiency of a computing system.

Some local memory devices (e.g., caches) include one or more victimcaches. A victim cache is an additional storage included in or connectedto a cache. Victim caches improve (e.g., reduce) the cache miss rate,and particularly reduce conflict misses, by storing data recentlyevicted from the corresponding cache. The addition of a victim cache canhave a similar impact on cache performance. The benefit is most evidentin cases when a victim cache is added to a direct mapped cache, becausea direct mapped cache has a relatively high rate of conflict misses.

Some examples disclosed herein include an improved data cache and victimcache architecture that reduces overall cache latency. In somealternative cache designs, a victim cache typically resides at the endof a cache controller. When a line is evicted out of the cachecontroller (e.g., removed to make room for additional data), instead ofremoving the data line and sending the evicted data line all the way tothe next level cache (e.g., L2) to be stored, the victim cache holds theevicted data line (e.g., victim data) until there is a reason to evictit out due to capacity or other reasons. In such a system, when asubsequent miss in the corresponding cache (e.g., L1 cache) occurs, thevictim cache can service the miss and return the line to thecorresponding cache, and thereby to a requesting processor core, so thatthe latency of read-miss is reduced. However, because some examplesystems include a victim cache in series with a main cache, the victimcache has to wait for the main cache to determine that the main cachedoes not have a data corresponding to a memory operation (also referredto herein as a memory instruction, memory request, and/or memorytransaction) from a CPU (e.g., a read operation, instruction, request,and/or transaction, a write operation, instruction, request, and/ortransaction, a read-modify-write operation, instruction, request, and/ortransaction, an atomic operation, instruction, and/or transaction, ahistogram operation, instruction, request, and/or transaction, etc.)before a victim cache can determine whether the memory address is storedin the victim cache. Examples disclosed herein include a cache systemthat decreases latency (e.g., increases speed), reduces the number ofcycles to perform write operations, atomic operations (e.g.,manipulating data stored in a location to increment, decrement, swapwith other data, etc.), and/or histogram operations (e.g., determine atotal number of each value in a cache line), and/or increases efficiencyof a computing system that includes a cache.

FIG. 1 illustrates an example computing system 100. The examplecomputing system 100 includes an example CPU 102, example processingcores 104 a-104 n, an example extended memory 106, and an example datacache 108. The example data cache 108 includes an example level one (L1)cache 110, an example level two (L2) cache 112, and an example levelthree (L3) cache 114. Although the example computing system 100 of FIG.1 includes N processing cores and three levels of cache. The examplecomputing system 100 may include any number of processing cores and/orlevels of cache. Additionally, one or more of the example components ofthe computing system 100 may be implemented on the same die and/ordifferent dies in the same chip and/or different chips.

The example CPU 102 of FIG. 1 includes the example processing cores 104a-104 n. The processing cores 104 a-104 n may be incorporated in thesame die or in separate dies (e.g., connected via one or moreinterfaces). The CPU 102 connects to the example data cache 108 via oneor more interfaces. For example, the example core 104 a of the exampleCPU 102 may be connected to the data cache 108 via a scalar interface(e.g., a 64-bit wide bidirectional and/or unidirectional interface)and/or a vector interface (e.g., a 512-bit wide interface). The use ofthe scalar interface and the vector interface may be based on interfaceutilization, data size, and/or other considerations. For example, ascalar read operation may be transmitted via the scalar data while thedata corresponding to the scalar read may be transmitted over the vectorinterface. Additionally, either the scalar interface and/or the vectorinterface may be used if the other interface is busy. In some examples,the CPU 102 may be connected to the data cache 108 using a differentnumber and/or different types of interfaces.

The processing cores 104 a-104 n of FIG. 1 access data from the exampleextended memory 106 and/or the example cache 108 to execute instructionsstored in the example extended memory 106 and/or the example data cache108. The example cores 104 a-104 n can execute different processes atthe same time to speed up the execution of tasks (e.g., instructions) ofthe computing system 100. For example, the cores 104 a-104 n may executeinstructions from a workload of an application by writing and/or readingdata to/from the extended memory 106 and/or the data cache 108. Becausethe data cache 108 includes a copy of some of the data stored in theexample extended memory 106, when one of the example cores 104 a needsto access (e.g., read and/or write) data from the extended memory 106,the example core 104 a transmits the read and/or write instructions tothe example data cache 108. As further described below, if the datacache 108 includes the data corresponding to the instructions from thecore 104 a (e.g., corresponding to a cache hit), the data cache 108fulfills the request and/or instructions from the processing core 104 a.If the data cache 108 does not include the data corresponding to theinstructions from the cores 104 a (e.g., corresponding to a cache miss),the data cache 108 interfaces with the example extended memory 106 toperform the transaction from the core 104 a.

The example extended memory 106 of FIG. 1 is connected to the exampledata cache 108 via an interface (e.g., a 1024-bit wide extended memoryinterface). However, a different number and/or a different type ofinterface may be additionally or alternatively used. The exampleextended memory 106 stores all the data that can be accessed for thecomputing system 100. The example extended memory 106 can be incorporateinto the computing system 100 and/or may be memory external to thecomputing system 100 (e.g., off-chip memory). In some examples, extendedmemory 108 interacts with a controller of the highest cache (e.g., theexample L3 cache 114), and the highest cache (e.g., L3 cache 114)interacts with the next highest cache (e.g., the example L2 cache 112),and so on. In such examples, the CPU 102 transmits memory operations tothe example L1 cache 110 and if the memory operation cannot be served bythe L1 cache 110, the L1 cache 110 transmits the memory operation to L2cache 112, and so on. In the example of FIG. 1, if the L3 cache 114(e.g., the highest level cache) cannot perform a read or writetransaction (e.g., because the memory address is not located in thelocal storage of the L3 cache 114), the L3 cache 114 interacts with theextended memory 106 to read or write the corresponding data to thememory address. The extended memory 106 may be on chip or off chipmemory (e.g., DDR) and the interface to the extended memory may be 2^(N)bits, where N depends on the type of extended memory used. In someexamples, there can be a prefetcher and/or preload mechanism in any ofthe data caches which can pull data from the example extended memory 106prior to execution of a problem to be stored locally at the cache beforethe CPU 102 executes any instructions, the memory 106 provides copies ofthe data stored in the memory to the example data cache 108. The datacache 108 may request additional information and/or instruct theextended memory 106 to adjust the stored data in the extended memory 106periodically, aperiodically, and/or based on a trigger, based oninstructions from the CPU 102.

The example data cache 108 of FIG. 1 stores blocks of data (e.g., acached subset of the data stored in the extended memory 106) from theexample extended memory 106 to reduce the time needed for the exampleCPU 102 to access the cached subset, thereby improving systemperformance. For best performance, attempts are made so that the data inthe data cache 108 corresponds to the data most likely to be used by theCPU 102. The data cache 108 provides access to the cached data whencalled upon by the CPU 102 during a cache hit (e.g., when the requesteddata is stored in the data cache 108). If the CPU 102 requests data thatis not included in the data cache 108 (e.g., a cache miss), the datacache 108 retrieves the corresponding data from the extended memory 106.For example, if the CPU 102 transmits a read operation for correspondingto a particular address of the extended memory 106, the data cache 108determines whether the data corresponding to the particular address ofthe extended memory 106 is cached in the data cache 108. If the datacache 108 determines that the data is cached, the data cache 108provides the data to the CPU 102 to be read. If the data cache 108determines that the data is not cached, the data cache 108 obtains thedata from the extended memory 106 and returns the data to the CPU 102.Additionally, the example data cache 108 may update the cached databased on the cache misses (e.g., to mitigate against future cachemisses). For write transactions from the CPU 102, the example data cache108 may temporarily store the corresponding data before providing it toupdate older data stored in the extended memory 106.

The example data cache 108 includes the example L1 cache 110, theexample L2 cache 112, and the example L3 cache 114. The levels of thecache may be based on speed and/or size. For example, the example L1cache 110 may be the fastest cache and smallest, followed by L2 112(e.g., slower than L1 110 but larger) and L3 114 (e.g., slower than L2112 but larger). Typically, the most commonly used data is stored in theL1 110 followed by the L2 112 and the L3 114. Accordingly, when the CPU102 calls for an address to be written to or read from, the instructionfrom the CPU 102 is first sent to the L1 cache 110 and, if thecorresponding data is not stored in the L1 cache 110, then theinstruction is sent to the L2 cache 112. If the corresponding data isnot stored in the L2 cache 112, the instruction is sent to the L3 cache114. If the corresponding data is not stored in the L3 cache 114, theexample data cache 108 accesses the data from the extended memory 106.

As further described below, the example L1 cache 110 of FIG. 1 includesa main cache and victim cache to execute instructions form the CPU 102in parallel. A victim cache stores victim data (e.g., data that wasevicted from the main cache to make room for new data corresponding toother address locations of the extended memory 106). In this manner,when there is a cache miss at the L1 level, the main L1 cache evicts afirst set of data (e.g., the victim data) to make room for a second setof data that corresponds to the transaction that caused the cache miss.The victim cache then stores the first set of data that was removed fromthe main cache to make room for the second set of data in the maincache.

FIG. 2 is an example block diagram of the L1 cache 110 of FIG. 1. Theexample L1 cache 110 includes an example CPU interface 202, example tagrandom access memory (RAM) accesses 204, 206, example tag RAM 208, 210,an example main cache store queue 212, an example main storage 214 (alsoreferred to as main cache storage or main cache), an example victimcache store queue 216, an example victim storage 218 (also referred toas victim cache storage or victim cache), an example cache controller220, an example main cache controller 222, an example victim cachecontroller 224, and an example L2 interface 228.

The example CPU interface 202 connects the CPU 102 (e.g., the core(s)104 a-104 n of the CPU 102) to the components of the L1 cache 110. TheCPU interface 202 is connected to the tag RAM accesses 204, 206 and thecache controller 220. The example CPU interface 202 receivesinstructions from the example core(s) 104 a-104 n of the example CPU102. The instructions may include, read instructions, writeinstructions, read-modify-write instructions, atomic instructions, etc.When the CPU interface 202 obtains instructions corresponding toparticular data stored at a particular address, the CPU interface 202interfaces with the cache controller 220 and the main tag RAM access 204to determine whether the corresponding data is stored in the mainstorage 214 and/or the victim storage 218 to perform the transaction.Additionally, for some types of transactions (e.g., read transactions)the example CPU interface 202 returns corresponding data to the exampleCPU 102. Furthermore, when the CPU interface 202 obtains instructionscorresponding to data at a particular address, the main components(e.g., the example main tag RAM access 204, the example tag RAM 208, theexample main cache store queue 212, the example main storage 214, andthe example main cache controller 222) and the victim components (e.g.,the example tag RAM access 206, the example tag RAM 210, the examplevictim cache store queue 216, the example victim storage 218, and theexample victim cache controller 224) operate in parallel (e.g., at thesame time) to determine whether data from the corresponding address isstored in the main storage 214 and/or the victim storage 218.

The example main tag RAM access 204 of FIG. 1 is coupled to the tag RAM208 and the cache controller 220. The victim tag RAM access 206 iscoupled to the tag RAM 210 and the cache controller 220. The main tagRAM access 204 accesses the tag RAM 208 to determine whether the datafrom a memory address corresponding to the instructions from the CPU 102is present in the main storage 214. The example victim tag RAM access206 accesses the tag RAM 210 to determine whether the data from a memoryaddress corresponding to the instructions from the CPU 102 is present inthe victim storage 218 in parallel with the main tag RAM access 204. Insome examples, the main tag RAM access 204 is implemented in the tag RAM208 and the victim tag RAM access 206 is implemented in the tag RAM 210.When the main tag RAM access 204 and/or the victim tag RAM access 206determines address(es) corresponding to the instructions from the CPU102 is/are present in the respective tag RAM 208,210, the main tag RAMaccess 204 and/or the victim tag RAM access 206 transmits the results(e.g., the determination and/or any corresponding data) to the examplecache controller 220.

In some examples, the main storage is directly mapped. Accordingly, insuch examples, a particular CPU memory address can only be stored at aparticular location of the main storage 214. Thus, the example tag RAM208 can potentially have a fixed memory address for the CPU instruction.In a directly mapped cache, a given address is stored at a particularlocation of the tag RAM 208.

The example tag RAM 208 of FIG. 2 is coupled to the example cachecontroller 220 and the example main storage 214. The example tag RAM 208stores a table that records the entries in the example main storage 214that correspond to memory addresses in the extended memory 106. In thismanner, the example main tag RAM access 204 can review the table todetermine if data corresponding to instructions from the CPU 102 isavailable in the main storage 214. The example tag RAM 210 is coupled tothe example cache controller 220 and the example victim storage 218. Theexample tag RAM 210 stores a table that records the entries in theexample victim storage 218. In this manner, the example victim tag RAMaccess 206 can review the table to determine if data corresponding toinstructions from the CPU 102 is available in the victim storage 218.When the data of the main storage 214 is updated, the example tag RAM208 may update the table to reflect any changes to the entries. Forexample, if the main storage 214 removes a first set of datacorresponding to a first memory address in the extended memory 106 andreplaces it with a second set of data corresponding to a second memoryaddress in the extended memory 106, the example tag RAM 208 updates thetable to reflect that the first set of data of the first memory addressis no longer stored in the main storage 214 and the second set of dataof the second memory address is now stored in the main storage 214.Likewise, when data from a first address location of the victim storage218 is changed to data from a second address location, the example tagRAM 210 may update the table to reflect any changes to the entries.

The example victim-side tag RAM 210 may be a content addressable memory(CAM). In some examples, the victim storage 218 is fully-associative(e.g., any location of the victim storage 218 can be used to store datafrom any CPU address). Thus, when the example CPU 102 provides a memoryaddress to the example L1 cache 110, the example victim tag RAM 210compares the provided memory address to all the entries of the tag RAM210. If there is a match between the provided address and the entriesstored in the tag RAM 210, then the address of the correspondinglocation in the victim storage 218 is output by the tag RAM 210. Theaddress is used to obtain the data from the victim storage 218 thatcorresponds to the CPU instruction.

The example main cache store queue 212 of FIG. 2 is coupled to theexample main storage 214 and the example cache controller 220. Theexample main cache store queue 212 is used when the CPU 104 issues astore operation (e.g., write operation, atomic compare and swap, atomicoperation, etc.). The example main cache store queue 212 can implementread-modify-write functionality. Read-modify-write functionalityincludes storing data in the local storages where there is a need tofirst read an older version of the data being written that is alreadypresent in the main storage 214 for reasons including updating errorcorrection code data. In this manner, while the read operation is beingperformed to get a copy of the older data from the main storage 214, thenew bit(s) included in the write portion of the read-modify-writetransaction from CPU 102 is/are buffered in the main cache store queue212. When the older data is available then only the new bit(s) which theCPU 102 is/are overwriting are updated in the store queue buffer and theupdated (e.g., merged) data is written back to the main storage 214. Forexample, the new bit(s) which the CPU 102 is/are overwriting from thewrite portion of the read-modify-write transaction (e.g., from the CPU102) including the corresponding memory address are buffered in the maincache store queue 212 until the old data of the corresponding write(e.g., store) instruction is read from the main storage 214. When thenew bit(s) included in the write portion of the read-modify-writetransaction are merged with the old data from the main storage 214, theupdated (e.g., merged) data is written back into the main storage 214.The extra pipelining for the store instructions provided by the maincache store queue 212 enables the instructions from the CPU 104 tocontinue execution when prior store instructions are waiting for loaddata from the main storage 214 to be available. In some examples, a mainstorage 214 includes SRAM, as further described below in conjunctionwith Sections 5 and 16. The example main cache store queue 212 isfurther described below in conjunction with FIGS. 3A, 3B, and 4.

The example victim cache store queue 216 of FIG. 2 is coupled to theexample victim storage 218 and the example cache controller 220. Theexample victim cache store queue 216 buffers data that is to be storedin the example victim storage 218. For example, victim values from storeinstructions (e.g., from the cache controller 220) including thecorresponding memory address and/or store data are buffered in thevictim cache store queue 216 until a prior or old value of thecorresponding store instruction is read from the victim storage 218.When stored bytes are merged with the prior/old data from the victimstorage 218, the value is written back into the victim storage 218.While the victim cache store queue 216 may process read, modify, and/orwrite operations from the cache controller 220 that were transmitted inresponse to a retirement point met (e.g., when one or more cache linesis removed from the L1 cache 110 to the L2 cache 112), in other examplesdisclosed herein, the victim cache store queue 216 may process read,modify, and/or write operations from the cache controller 220 that weretransmitted directly from the CPU 102. The example victim cache storequeue 216 is further described below.

The example main storage 214 of FIG. 2 is coupled to the example tag RAM208, the example main cache store queue 212, and the example cachecontroller 220. The example main storage 214 stores data (e.g., entries)that correspond to data in memory address locations in the extendedmemory 106. The main storage 214 stores that data that has a highprobability of being called upon by the example CPU 102. The stored datamay be updated when, for example, the CPU 102 attempts to access (e.g.,read, write, etc.) data that is not cached in the example main storage214. The example main storage 214 may be or include static RAM (SRAM)and/or any other type of storage which provides a single cycle access tostored data.

The example victim storage 218 of FIG. 2 is coupled to the example theexample tag RAM 210, the example victim cache store queue 216 and theexample cache controller 220. The example victim storage 218 stores data(e.g., entries) corresponding to memory address locations that have beenremoved from the example main storage 214 to make room for data fromother address locations that the CPU 102 more recently accessed or ismore likely to access. The example victim storage 218 may be or includea register file, static RAM (SRAM), and/or any other type of storage.

In operation, initially, the example main storage 214 stores data fromdifferent addresses in the example extended memory 106 based onlikelihood of use. If the example CPU 102 sends an instructioncorresponding to a memory address that is stored in the main storage214, the example cache controller 220 controls the components to performthe transaction. For example, the cache controller 220 may transmit aninstruction to the main cache store queue 212 for subsequent processingand storage in the main storage 214. If the example CPU 102 sends aninstruction corresponding to a memory address that is not stored in themain storage (e.g., stored in the victim storage 218), the example mainstorage 214 may store the data at the corresponding memory address afterthe data is retrieved from another storage. To make room for the data,the main storage 214 removes some data corresponding to one or morememory address locations. The removed data and corresponding memoryaddress locations are called victims or evicted lines. The selection ofwhich data is to be a victim is based on various parameters according toa replacement policy. After being removed from the main storage 214, thevictim is stored in the example victim storage 218. If the victimstorage 218 is full, the victim storage 218 removes data (e.g., a secondvictim) to make room to store the victim from the main storage 214.After the second victim is removed from the victim storage 218, thesecond victim is transmitted to L2 cache 112 for storage.

Although the example L1 cache 110 of FIG. 1 includes one main cachestore queue 212 with corresponding main storage 214 and one examplevictim cache store queue 216 with corresponding victim storage 218, theexample main cache store queue 212 and/or the example victim cache storequeue 216 may include multiple store queues corresponding to multiplestorages. For example, the main storage 214 and/or the victim storage218 may be divided into a plurality of independently addressable banks(e.g., into any number of storage devices with any number of linewidths, rows, etc.), where individual banks may have its owncorresponding store queue. For example, a main storage 214 made up of256 rows with each row having a line width of 1024 bits may be dividedinto 16 main storages (e.g., banks) with 64 bits per row in a particularbank, where each bank may have their own main store queue. In such anexample, if vector data for a read and/or write request that hits the L1cache 110 is 512 bits wide, the cache controller 220 may process therequest as 8 parallel writes and/or reads to the 8 banks. In such amulti-bank set up, the read and/or write operations may be sent to thebanks in parallel and the banks arbitrate their own process in responseto the read and/or write operations. By operating independently,operation of the multi-bank approach is more efficient than a singlemain storage (e.g., because the entire cache line is not locked up whena request is received and only a portion of the cache line allocated tothe bank that received such a request would be locked), at the expenseof complication and/or parts.

The example cache controller 220 of FIG. 2 is coupled to the componentsof the L1 to control how data is read and/or written in the examplestorages 214, 216, and/or how data is updated in the example storages214, 218. For example, when a read request, a write request, an atomicrequest, a read-modify-write request, etc. is received at the exampleCPU interface 202, the cache controller 220 obtains the request andinstructs the other components accordingly. For example, during a readrequest for data at a particular location of the extended memory 106,the example cache controller 220 instructs the main tag RAM access 204to access the tag RAM 208 to determine if the main storage 214 isstoring the data corresponding to the location of the extended memory106 from the read request. If the main tag RAM access 204 determinesthat the entry is located in the main storage 214 (e.g., a cache hit),the cache controller 220 determines the location of the particular entrybased on the data in the tag RAM 208 and interfaces with the main cachestore queue 212 to read the value from the example main storage 214 andreturns the value to the CPU 102 via the CPU interface 202. The examplecache controller 220 includes the main cache controller 222 to controlthe main cache components (e.g., the example main tag RAM access 204,the example tag RAM 208, the example main cache store queue 212, and theexample main storage 214) and the example victim cache controller 224 tocontrol the victim cache components (e.g., the example victim tag RAMaccess 206, the example tag RAM 210, the example victim cache storequeue 216, and the example victim storage 218) in parallel with the maincache controllers 222 control of the main cache components. In someexamples, the cache controllers 222, 224 may be separate controllersand/or combined to operate in a single controller.

The example cache controller 220 of FIG. 2 interfaces with the exampleL2 interface 228 to obtain data to be stored in the example main storage214 (e.g., initially, after a cache miss, etc.). Additionally, theexample cache controller 220 may transmit updates to the data of themain storage 214 and/or the victim storage 218 to the L2 cache 112 whennew data is written (e.g., when old data is written over), so that readinstructions from the CPU 102 are propagated to the L2 cache 112 via theL2 interface 228. The example cache controller 220 interfaces with theexample L2 interface 228 to transmit and/or receive data from the L2cache 112 and/or the L3 cache 114 (e.g., directly or via the L2 cache112). For example, when the main storage 214 and the victim storage 218do not include a memory address location for data corresponding toinstructions from the CPU 102 (e.g., corresponding to a cache miss), theexample cache controller 220 transmits the instruction to the example L2cache 112 via the L2 interface 228. The cache controller 220 may receivethe corresponding data from the L2 cache 112 via the L2 interface 228 ifthe data is stored in the L2 cache 112 or the L3 cache 114. In such anexample, the cache controller 220 may store the correspondinginformation from the L2 cache 112 in the main storage 214. In someexamples, when the victim storage 218 has to remove data for aparticular location (e.g., an old victim) to make room for a new victimfrom the main storage 214, the example cache controller 220 may transmitthe old victim to the L2 cache 112 via the L2 interface 228 to be storedin the L2 cache.

FIGS. 3A-3D illustrate an example circuit implementation of the L1 cache110 of the example computing system 100 of FIG. 1. The exampleimplementation of FIGS. 3A-3D includes the example CPU interface 202,the example tag RAMs 208, 210, the example main cache store queue 212,the example main storage 214, the example victim cache store queue 216,the example victim storage 218, and the example cache controller 220 ofFIG. 2. The example implementation of FIGS. 3A-3D further includes anexample modify, exclusive, shared, invalid (MESI) RAM 300, exampleaddress processing components 302 a-c, example bank processing logic303, example hit/miss comparison logic 304, 306, an example replacementpolicy component 308, an example flush engine 309, an example errorcorrecting code (ECC) logic 310, 312, example data multiplexer (MUX)circuits 314, 316, an example MUXs 318, 320, and example latches 322.

In the example implementation of FIGS. 3A-3D, the example CPU interface202 includes two interfaces (e.g., one scalar and one vector interface,both interfaces having two parts, one for input data from the CPU 102and one for output data to the CPU 102). The input CPU interface 202 ofFIGS. 3A-3D includes an elastic buffer to buffer incoming data from theCPU 102, a multiplexer to select between the buffered data from anelastic buffer in case there are pending CPU instructions in the elasticbuffer and instructions coming directing from the CPU 102 in case theelastic buffer queue is empty, and breaks the incoming instructions intothe corresponding address, operation (e.g., read, write, etc.) and writedata (e.g., if the instructions correspond to a write operation). Theoutput CPU interface 202 of FIGS. 3A-3D transmits data back to the CPU102.

The example main cache store queue 212 of FIGS. 3A-3D includes blocksthat correspond to operations of the main cache store queue 212. Forexample, the main cache store queue 212 includes blocks to implement aread-modify-write operation, write merging, write data forwarding,writing operation, complete parity block write data, weighted histogramoperations, load and increment operations, and compare and swapoperations. The example main cache store queue 212 is further describedbelow in conjunction with FIG. 4A. The example main cache store queue212 operates in conjunction with the example main storage 214. In theexample of FIGS. 3A-3D, the main storage 214 is data RAM (DRAM).

The example victim cache store queue 216 of FIGS. 3A-3D includes blocksthat correspond to operations of the victim cache store queue 216. Forexample, the victim cache store queue 216 includes blocks to implement aread-modify-write operation, write merging, write data forwarding,writing operation, complete parity block write data, load and incrementoperations, and compare and swap operations. The example victim cachestore queue 216 is further described below in conjunction with FIG. 5.The example victim cache store queue 216 operates in conjunction withthe example victim storage 218. In the example of FIGS. 3A-3D, the mainstorage 214 is a register file.

The example MESI RAM 300 of FIGS. 3A-3D is connected to the command lineof the example CPU interface 202 and the example DRAM 214. The exampleMESI RAM 300 tracks the state of the data in the example main storage214 based on the command from the CPU 102. For example, the MESI RAM 300tracks the states of a cache line by marking the cache line as modified,exclusive, shared, or invalid. Modified, or dirty, corresponds to whenthe cache line contains data that is not stored in any othersimilar-level cache and the data has been modified from the value inmain memory (e.g., so that a read of the data in extended memory 106 isflagged or permitted because it is not up-to-date or valid). Exclusiveis when the cache line contains data that is not stored in any othersimilar-level cache and the data is clean (e.g., matches the data in theextended memory 106). Shared indicates that the cache line contains datathat may be stored in other caches and is clean (e.g., the line may bediscarded because it is present in another cache). Invalid indicatesthat the cache line is invalid or unused. The MESI RAM 300 may be calledupon when updates to the main storage 214 and/or the extended memory106. The example MESI RAM 300 for victim cache is implemented inconjunction with the example tag RAM 210.

The example MESI RAM 300 of FIGS. 3A-3D adds coherency to the system bytracking, labelling, marking, etc. The status of a memory address mayprevent data writes at particular times so that data mismatches do notoccur at different levels of cache. The state tracked by the MESI RAM300 may be transmitted with cache misses so that the higher level cacheunderstands what the data at the memory address will be used for. Forexample, if the L1 cache sends out a cache miss for a read operation,the cache miss includes the shared state to let the high level cacheknow that the data will be read but not manipulated. If the L1 cache 110sends out a cache miss for a write operation, the cache miss includes anexclusive state to let the higher level cache know that the data will bemodified. When the example main storage 214 and/or the victim storage218 evicts a victim, the status from the example MESI RAM 300 may beused to figure out how to evict. For example, if the data is shared, themain storage 214 and/or victim storage 218 can simply discard (e.g.,because the data at memory address already located in a high cache). Ifthe data is exclusive or modified, the cache controller 220 instructsthe interface 228 to transmit the victim to the higher level cache(e.g., because the data for the memory address is not located in higherlevel cache or is located in higher level cache but is outdated).

The example address processing components 302 a-c of FIGS. 3A-3D areconnected to the CPU interface 202, the example main storage 214, theexample main cache store queue 212 (e.g., via the MUX 318), the examplevictim storage 218 (e.g., via the example MUX 320) and each other. Theexample address processing components 302 a-c include an example firstaddress processing component 302 a, a second address processingcomponent 302 b, and a third address processing component 302 c. Thefirst address processing component 302 a performs address translation,the second address processing component 302 b performs data rotation,and the third address processing component 302 c facilitates bankorganization. Alternatively, one or more of the first address processingcomponent 302 a, the second address processing component 302 b, and thethird address processing component 302 c can be included in the samehardware, logic circuit, integrated chip, etc. The example addressprocessing components 302 a-c organizes data to be written into theexample main storage 214 and the victim storage 218 according to aparticular storage protocol to ensure that the data is stored correctly.For example, in a multi-bank example (e.g., where the main cache storequeue 212, the main storage 214, the victim cache store queue 216, andthe victim storage 218 are broken up into multiple banks), the addressprocessing components 302 a-c may use a memory address from a CPUoperation to determine which banks of the main cache store queue 212,the main storage 214, the victim cache store queue 216, and the victimstorage 218 is broken up into multiple banks would be needed for thegiven CPU operation.

The example bank processing logic 303 is coupled to the CPU interface202, the example main storage 214, the example main cache store queue212 (e.g., via the MUX 318), and the example victim storage 218 (e.g.,via the example MUX 320). In operation, the bank processing logic 303 isconfigured to analyze read, modify, and/or write instructions from theCPU interface 202. In this manner, the bank processing logic 303 isconfigured to determine the nature of the read, modify, and/or writeinstructions to facilitate efficient partial bank read, modify, and/orwrite instructions. In examples disclosed herein, the bank processinglogic 303 detects whether incoming write instructions indicate a writeof an entire bank, or a write of a partial bank. In this manner, thebank processing logic 303 can indicate whether to operate aread-modify-write operation, while negating to transmit the readinstruction. Example description of bank processing logic 303 operationis described below.

The example hit/miss comparison logic 304 of FIGS. 3A-3D is connected tothe input CPU interface 202, the tag RAM 208, the main storage 214, themain cache store queue 212, the cache controller 220, and/or the exampleMUX circuit 314 (e.g., via a data forward latch). The hit/misscomparison logic 304 obtains the address from the tag RAM 208 and anaddress of the instruction from the CPU 102 and compares the two (e.g.,using exclusive nor (XNOR) logic) to determine whether the address fromthe instruction hit or missed (e.g., the data corresponding to theaddress is stored in the example DRAM 214 or not). The example hit-misscomparison logic 304 includes TAG compare logic to output the result ofthe comparison to the example main cache store queue 212, the examplecache controller 220, and/or to the example MUX circuit 314.

The example hit/miss comparison logic 306 of FIGS. 3A-3D is connected tothe input CPU interface 202, the tag RAM 210, the victim cache storequeue 216, and/or the example replacement policy component 308. Thehit/miss comparison logic 306 obtains the entry number of the victimcache (e.g., location) from the tag RAM 210 and an address from theinstruction from the CPU interface 202 and compares the two to determineif the access (e.g., the instruction from the CPU interface 202) is ahit or miss (e.g., the data corresponding to the address is stored inthe example victim storage 218 or not). The example hit-miss comparisonlogic 306 outputs the result to the replacement policy component 308,the address encoder 326, the multiplexer 330, and/or the victim cachestore queue 216.

The address encoder 326 of FIGS. 3A-3D is connected to the tag RAM 210(via the hit/miss comparison logic 306) and a multiplexer 330. Theaddress encoder 326 encodes an address of the tag RAM 210 to a form thatis interpretable by the victim storage 218. For example, the tag RAM 210may store 16-bit memory addresses while the victim storage 218 stores4-bit memory addresses corresponding to the 16-bit memory addresses.Thus, the address encoder 326 may transform the 16-bit memory addressinto a 4-bit memory address to locate and/or enter the correspondingmemory address in the victim storage 218. Additionally and/oralternatively, the address encoder 326 encodes the memory address intoany bit value. The address encoder 326 is coupled to an examplemultiplexer 330, such that the address encoder 326 provides the encodedaddress to the multiplexer 330.

The example replacement policy component 308 of FIGS. 3A-3D is connectedto the hit-miss comparison logic 306 and a replacement address encoder328. In some examples, the replacement policy component 308 is connectedto the tag RAM 210. The example replacement policy component 308controls the replacement policy of data stored in the example victimstorage 218 (e.g., which data to move out of the victim cache in theevent that a new victim is to be stored in the victim storage 218). Insome examples, there may be a replacement policy component for theexample main storage 214. However, a replacement policy is not requiredfor a direct mapped cached (e.g., if the example main storage 214 isdirectly mapped because a particular address will only go in onelocation). The example flush engine (e.g., the flush engine component)309 is coupled to the replacement policy 308. In some examples, theflush engine 309 is used and/or otherwise invoked to flush out writemisses stored inside the victim storage 218 at a pre-definedperiodicity.

The replacement address encoder 328 of FIGS. 3A-3D is coupled to themultiplexer 330, such that the replacement address encoder 328 providesthe encoded replacement address to the multiplexer 330. The replacementaddress encoder 328 encodes an address selected by the replacementpolicy component 308. For example, the replacement policy component 308outputs a 16-bit replacement memory address to the replacement addressencoder 328, and the replacement address encoder 328 transforms the16-bit replacement memory address to a 4-bit replacement memory address.Additionally and/or alternatively, the replacement address encoder 328encodes the replacement memory address into any bit value.

The multiplexer 330 of FIGS. 3A-3D is connected to the hit/misscomparison logic 306, the address encoder 326, the replacement addressencoder 328, and an address read 332. The multiplexer 330 selects anencoded address based on the result of the hit/miss comparison logic 306(e.g., based on whether the access was a hit or miss). The multiplexer330 provides the selected memory address to the address read 332 to beread into the victim storage 218. For example, the multiplexer 330outputs the location of the victim storage 218 which the CPU instructionmay use to either read the data from or store the data in case of awrite instruction.

The example error correcting code (ECC) logic 310 of FIGS. 3A-3D isconnected to the example main storage 214 via the latch 322, and theMUXing circuit 314. If the example L1 cache 110 supports ECC memory, theexample main storage 214 stores data in blocks along with a set of ECCsyndrome bits that correspond to the blocks. When a read operation isreceived, the example main storage 214 may provide the stored data blockand the corresponding ECC syndrome bits to the ECC logic 310. Theexample ECC logic 310 may regenerate the ECC syndrome bits based on thedata block as read from the main storage 214 and compare the regeneratedECC syndrome bits with the previously stored bits. The example ECC logic310 may determine that a data block has been incorrectly read when thereis a discrepancy and may correct the error in the data block.

The example error correcting code (ECC) logic 312 of FIGS. 3A-3D isconnected to the example victim storage 218 via the latch 324, and theMUX circuit 316. The example ECC logic 312 performs ECC correction logicin a similar manner as the example ECC logic 310. However, the exampleECC logic 312 performs the ECC syndrome bit comparison with respect tothe example victim storage 218.

The example main data MUX circuit 314 of FIGS. 3A-3D is connected to themain cache store queue 212, the ECC logic 310, the output of thehit/miss comparison logic 304 (e.g., via a latch), the example outputCPU interface 202 (e.g., via the example latch 322), the example victimdata MUX 316, and the example cache controller 220. The example maindata MUX circuit 314 has the reverse operation of the example addressprocessing components 302 a-c to convert the data in the data address tobe transmitted to the example CPU 102. The MUXs within the example MUXcircuit 314 are controlled by the cache controller 220 via therespective select inputs.

The example victim data MUX circuit 316 of FIGS. 3A-3D is connected tothe victim cache store queue 216, the ECC logic 312, the example maindata MUX circuit 314, the L2 cache 112 (e.g., via a latch), and theexample cache controller 220. The example main data MUX circuit 314 hasthe reverse operation of the example address processing components 302a-c to convert the data in the data address to be transmitted to theexample CPU 102. The MUXs within the example MUX circuit 316 arecontrolled by the cache controller 220 via the respective select inputs.

The example MUX 318 of FIGS. 3A-3D is connected to the L2 cache 112, theexample CPU interface 202 via a latch, the address processing components302 a-c, the main cache store queue 212, the main storage 214, and thecache controller 220. The example cache controller 220 controls the MUX318 to control all the ways that data could be written into or read fromthe example main storage 214 (e.g., via direct memory access (DMA), asnoop transaction (e.g., when the L2 cache 112 wants data from the L1cache 110), the main cache store queue 212, the read hit buffer, etc.).The example MUX 320 is connected to the example main storage 214 (e.g.,via the eviction line for storing victims), the address processingcomponents 302 a-c (e.g., via the write-stream and/or CPU load), theexample L2 cache 112 (e.g., via the L2 W and/or snoop lines), the victimstorage 218, and/or the cache controller 220. The example cachecontroller 220 controls the MUX 320 to control all the ways that datacould be written into or read from the example victim storage 218 (e.g.,via direct memory access (DMA), a snoop transaction, the victim cachestore queue 216, an eviction from the example main storage 214, via L2cache 112, etc.). The example MUXs 318, 320 are controlled by theexample cache controller 220 via the respective select inputs.

The elements of FIGS. 3A and 3B are arranged in a manner representingthe flow of transaction processing. The temporal elements arerepresented by stages E1-E5. Each stage represents a discrete period oftime, and in some examples each stage represents a clock cycle or aninteger number of clock cycles.

Write Miss Caching in L1 Data Cache

In operation, the example CPU 102 transmits instructions (e.g., returnsdata based on a read operation, write data to a particular memorylocation). The first time the example CPU 102 requests data for aparticular memory address, if the data for the memory address is notstored in the main storage 214, the tag ram 208 will output a read missand the L1 cache will send the read miss information out (e.g., to L2cache 112, L3 cache 114, and/or the extended memory 106) to be serviced(e.g., return the data corresponding to the address of the request fromthe CPU 102). The L1 cache 110 may then perform a read allocate. A readallocate is when the L1 cache 110 stores the data in the main storage214, updates the tag RAM 208, etc., to identify that the data for theaddress is now stored in the main data storage. The L1 cache 110 mayreturn the data to the CPU 102 and/or wait for the CPU 102 to send out asubsequent read request for the same address. If the CPU 102 sends out asubsequent read request for the same address, the tag RAM 208 willidentify that the data for the address is now present in the mainstorage 214, thereby resulting in a read hit. If the CPU 102 does awrite to the same address, the tag RAM 208 will identify a write hitbecause the address is stored in the main storage 214. For a write hit,the CPU 102 will provide data to write, and the L1 cache 110 will writethe data into the main storage 214 corresponding to the address.

If the initial action from the CPU 102 (or a subsequent action from theCPU 102) resulted in a write miss (e.g., the memory address that the CPU102 is attempting to write to is not stored in the example mainstorage), the L1 cache 110 can perform a write miss. During a writemiss, the L1 cache 110 sends the write miss out to the higher levelcache (e.g., L2 cache 112, L3 cache 114, etc.) and/or extended memory106 to retrieve the data from the memory address, stories the data inthe main storage 214, and then writes the data from the CPU 102 in themain storage 214 at a location corresponding to the memory address.

However, when the CPU 102 performs a write operation, it typically doesnot need the information that it has written right away. Accordingly,some example cache systems included a write buffer to store writeinstructions from the CPU to prevent stalling the CPU (e.g., byattempting to load memory address from higher cache before writing thedata). In this manner, the CPU can continue to send instructions whilethe L1 cache interfaces with higher level cache to obtain the data inthe memory address corresponding to the write instructions in thebuffer, and stores the data in the main storage and writes the data(e.g., stored in the write buffer) in parallel with subsequentinstructions from the CPU. However, the CPU may only write a few numberof bytes per write instruction and the interface between the L1 cacheand higher level caches and/or the extended memory is capable of sendinga larger number of bytes (e.g., 64 byte bandwidth). Accordingly, thetransmission of a few number of bytes per cycle on a large byteinterface is inefficient.

In the system of FIGS. 3A-3D, instead of implementing a write buffer, asection of the victim storage 218 is dedicated for write-missinformation. Accordingly, the example victim storage 218 is a victimcache and a write miss buffer. The section of the victim storage iscalled the write miss cache. In some examples, the write miss cache maybe additionally or alternatively implemented in the main storage 214. Insome examples, the write miss cache is a 128 bytes of a cache line. Thewrite miss cache stores all the write miss data until the write misscache is full and/or there is more than a first threshold number ofbytes that can be sent to higher level cache and/or extended memory.Once the write miss cache is full or the first threshold amount of writemiss data has been added to the write miss cache, the victim storage 218combines a second threshold amount of the write miss data in the writemiss cache into one signal that is sent to the higher level cache (e.g.,via the example L2 interface 228) to be written in the address stored inthe higher level cache (e.g., the L2 cache 112) and/or the extendedmemory 106. In this manner most or all of the bandwidth of the interfacecan be utilized in a particular cycle. The second threshold may be thesame as or different than the first threshold. Additionally, the writedata is stored locally in the main storage 214 or the victim storage218. Thus, if an additional read or write operation is sent from the CPU102 prior to the write operation being passed to the higher cache (e.g.,the L2 cache 112, the example L3 cache 114, etc.) and/or the extendedmemory 106, the cache controller 220 can read and/or write the data tothe corresponding address within the write miss cache before it getstransmitted to higher level cache and/or the extended memory 106.

In some examples, the structure of the write miss cache in the victimstorage 218 includes a byte enable register file that represents thevalue bytes (e.g., the bytes to be written) of the write missinformation. For example, if a write miss corresponding to writing datafor a first byte and a third byte of a memory address is stored in thewrite miss cache, the victim storage 218 stores the write miss data forthe first and third byte in conjunction with the memory address andpopulates the corresponding entry of byte enable register file with afirst value (e.g., ‘1’) for the elements of the entry that correspond tothe first and third byte and a second value (e.g., ‘0’) for theremaining elements of the entry. In this manner, when the write missdata is sent to higher level cache, the byte enable bits of the entryare included in the transmission so that the higher level cache knowswhich data is valid (e.g., which bytes are to be written to) and whichdata is invalid (e.g., which bytes should not be written to).

In certain cases, if a read or a write request is a hit in the mainstorage 214, the results of the victim storage 218 may be disregarded.Where the main storage 214 is configured as a one way associative cache,cache request conflicts as with multiple datapaths are straight forward.A datapath is one or more logic circuits that, when executed and/orotherwise invoked, effectuate the transmission or delivery of data(e.g., logic signal(s), bit vector(s), etc.) from a source to adestination. Cache request conflicts from the multiple datapaths may bean issue for the victim storage 218 where the victim storage 218 isfully associative and can store write-miss entries as well as cacheentries. Cache request conflicts for two datapaths may be handled asdescribed in the following examples. Of note, in the following examples,cache operations are described in the context of a particular datapath.However, it may be understood that the examples are directed tocombinations of particular cache operations, and which datapath aparticular cache operation is on does not matter.

In a first example, there is a cache read miss for a first datapath anda cache write hit for a second datapath, with two different memoryaddresses. In certain cases where the victim storage 218 is fullyassociative, cache requests can go to any location within the victimstorage 218. Referring to FIGS. 3A-3D, address generation for a locationwithin the victim storage 218 occurs in the E2 pipestage along withaddress lookup in the victim cache tag RAM 210, thus address generationfor a location within the victim cache is performed before it is knownwhether an address of the cache request is a hit or miss. After thecontroller 220 determines that there is a read miss on the main storage214, a request to obtain the memory address of the read request isissued to a higher level cache or memory. Where the main storage 214 isone way associative, the memory address of the read request of the firstdatapath maps to a single location in the main storage 214. If there isalready cached data in the single location, the already cached data isevicted from the main storage 214 to the victim storage 218 to thepre-generated location within the victim storage 218. If thispre-generated location is the same location the cache write of thesecond datapath is a hit on, a conflict occurs. This conflict may bedetected by the cache controller 220. As indicated above, addressgeneration for a location within the victim storage 218 occurs before itis known whether the address of cache request is a hit or a miss, thusthere is an address generated for a second location within the victimstorage 218 for the cache write of the second datapath prior to thedetermination that the cache write is a hit. Based on the detection ofthe conflict, this second location within the victim cache may be usedto store the data evicted from the main storage 214 by the read miss.

In another example, there may be a cache read miss for the firstdatapath and a cache write hit for the second datapath, as with thefirst example. In this example, due to the read miss, a request toobtain the memory address of the read request is issued to a higherlevel cache or memory and the already cached data is evicted from themain storage 214 to the victim storage 218 to a pre-generated location,here location A, within the victim storage 218. In this example, thecache write of the second datapath hits on location A within the victimstorage 218 as well, resulting in a set conflict. One possible solutionto such a conflict is to load the requested read miss from the higherlevel cache or memory directly to the victim cache in a separatelocation. Another solution to the conflict is for the cache controller220 to stall the read miss such that the already cached data is notevicted to the victim storage 218 until after the cache write of thesecond datapath completes to location A and location A is evicted to ahigher level cache or memory. In certain cases, the stall may occurwhile waiting for the higher level cache or memory to return the readmiss data.

As another example, a first cache write may be received on the firstdatapath for the victim storage 218 and a second cache write is alsoreceived on the second datapath for the victim storage 218. If the firstcache write and the second cache write are addressed to different memoryaddresses, then both cache writes may proceed in parallel to the victimstorage 218. If the first cache write and the second cache write areboth addressed to the same memory address and both are cache misses,then the victim cache controller 224 allocates a single location in theallocated victim cache write-miss memory and merges the first cachewrite and the second cache write in the victim cache store queue 216.The merged data may then be written to the victim cache write-missmemory along with merged byte enable, priority, and color taginformation. If the first cache write and the second cache write areboth addressed to the same memory address and both are cache hits, boththe first cache write and the second cache write are merged into thecache at the hit location.

As another example a cache read may be received on the first datapathfor the victim storage 218 and a cache write may be received on thesecond datapath for the victim storage 218. In the cases where the cacheread is a hit and the cache write is a hit to different locations in thevictim storage 218, the cache read and cache write proceed in parallelwithout conflicts. In the case the cache read is a hit and the cachewrite is a miss to different locations in the victim storage 218, thecache read and cache write also proceed in parallel without conflicts.In the case the cache read is a miss and the cache write is a hit todifferent locations in the victim storage 218, the cache read may use anaddress generated for a location within the victim storage 218 for thecache write as discussed above. In the case the cache read is a miss andthe cache write is a miss to different locations in the victim storage218, both the cache read and the cache write use addresses generated forlocations within the victim storage 218.

In another example, a cache read may be received on the first datapathfor the victim storage 218 and a cache write may be received on thesecond datapath for the victim storage 218. In certain cases, the cacheread may be a hit for a first address of a set of addresses stored inthe victim storage 218. The cache write may also be a hit for a secondaddress of the same set of addresses stored in the victim storage 218.In such a case, the cache read and the cache write may proceed inparallel without conflicts. In another case, the cache read may be a hitfor a first address of a set of addresses stored in the victim storage218. The cache write may be a miss for a second address of the same setof addresses stored in the victim storage 218. In such a case, the cacheread and the cache write may proceed in parallel without conflicts. Inanother case, the cache read may be a miss for a first address of a setof addresses stored in the victim storage 218. The cache write may be ahit for a second address of the same set of addresses stored in thevictim storage 218. In such a case, as similar to that discussed above,the cache read may be stalled until after the cache write of the seconddatapath completes to the location in the victim storage 218 and isevicted to a higher level cache or memory. The cache read then proceedsto read the set of addresses from the higher level cache or memory intothe victim storage 218. In another case, the cache read may be a missfor a first address of a set of addresses stored in the victim storage218. The cache write may also be a miss for a second address of the sameset of addresses stored in the victim storage 218. In such a case, thecache read and the cache write may proceed in parallel withoutconflicts.

In another example, a cache read may be received on the first datapathfor the victim storage 218 and a cache write may be received on thesecond datapath for the victim storage 218. In certain cases, the cacheread may be a hit for an address stored in the victim storage 218. Thecache write may also be a hit for the same address stored in the victimstorage 218. In such a case, the cache read may proceed first and thecache write may be stalled until after the cache read completes.Alternatively, the order of the cache write and cache read may be basedon the datapath on which the cache write and cache read are received,with the cache operation arriving on a lower (or higher) numbereddatapath being completed before the other cache operation. In certaincases, the cache read may be a miss for an address stored in the victimstorage 218. The cache write may also be a miss for the same addressstored in the victim storage 218. In such a case, the cache writeoperation may be forwarded to a higher level cache or memory and thenthe cache read may obtain the data from the higher level cache or memoryafter the cache write operation completes for storage into the victimstorage 218.

In another example, a first cache read may be received on the firstdatapath for the victim storage 218 and a second cache read may bereceived on the second datapath for the victim storage 218. If the firstcache read and the second cache read are for different memory addresses,then there are no conflicts for either hits nor misses. In certaincases, the first cache read may be a miss for a first address of a setof addresses. The second cache read may also be a miss for a secondaddress of the same set of addresses. If the first cache read and thesecond cache read have different priority levels, a higher level cacheor memory is accessed based on the higher of the different prioritylevels. Otherwise, the higher level cache or memory is accessed and theset of memory addresses obtained for storage in the victim storage 218.The case where the first cache read and the second cache read are forthe same address is handled identically.

Example methods, apparatus, systems, and articles of manufacture tofacilitate Write Miss Caching in L1 data cache are disclosed herein.Further examples and combinations thereof include the following: Example1 includes an apparatus comprising a first cache storage, a second cachestorage, wherein the second cache storage includes a first portionoperable to store a first set of data evicted from the first cachestorage and a second portion, a cache controller coupled to the firstcache storage and the second cache storage and operable to receive awrite operation, determine that the write operation produces a miss inthe first cache storage, and in response to the miss in the first cachestorage, provide write miss information associated with the writeoperation to the second cache storage for storing in the second portion.

Example 2 includes the apparatus of example 1, wherein the cachecontroller is operable to compare the second portion of the second cachestorage to a threshold, and based on the second portion exceeding thethreshold, cause the write miss information to be transmitted to asecond cache.

Example 3 includes the apparatus of example 2, wherein the thresholdcorresponds to a bandwidth of an interface.

Example 4 includes the apparatus of example 2, wherein the thresholdcorresponds to a size of the second portion.

Example 5 includes the apparatus of example 1, wherein the write missinformation is first write miss information, the cache controlleroperable to the second cache storage is to not provide the first writemiss information from the first cache storage to the second cachestorage if the second cache storage includes second write missinformation for a memory address corresponding to the first write missinformation.

Example 6 includes the apparatus of example 1, wherein the first cachestorage and the second cache storage are connected in parallel to acentral processing unit.

Example 7 includes the apparatus of example 1, wherein the write missinformation is first write miss information, the cache controlleroperable to, when a first memory address of the first write missinformation from the first cache storage matches a second memory addressof second write miss information stored in the second portion, to mergethe first write miss information with the second write miss information.

Example 8 includes the apparatus of example 7, wherein the cachecontroller is to merge the first write miss information with the secondwrite miss information by at least one of (a) maintaining first writeinformation of the first write miss information or (b) discarding secondwrite information of the second write miss information when the secondwrite information corresponds to the same one or more bytes as the firstwrite miss information.

Example 9 includes the apparatus of example 1, wherein the secondportion includes a byte enable register, the cache controller to storevalues in the byte enable register based on the write miss information.

Example 10 includes the apparatus of example 9, wherein the valuescorrespond to elements of the write miss information that will bewritten.

Example 11 includes a system comprising a central processing unit tooutput a write command corresponding to a memory address, a first cachestorage to output write miss information from a first storage to asecond storage when the first cache storage does not store data for thememory address, and a second cache storage, wherein the second cachestorage includes a first portion operable to store a first set of dataevicted from the first cache storage and a second portion, the secondcache storage to store the write miss information in a dedicated sectionof the second storage, the dedicated section being dedicated to thewrite miss information.

Example 12 includes the system of example 11, wherein the second cachestorage is to, when the dedicated section has more than a thresholdamount of write miss information, output the write miss information to asecond cache.

Example 13 includes the system of example 12, wherein the thresholdcorresponds to a bandwidth of an interface to the second cache.

Example 14 includes the system of example 12, wherein the thresholdcorresponds to a size of the second portion.

Example 15 includes the system of example 11, wherein the second cachestorage is to not store the write miss information from the firststorage in the second portion if the second cache storage includessecond write instructions corresponding to a same memory address as thewrite miss information from the central processing unit.

Example 16 includes the system of example 11, wherein the first cachestorage and the second cache storage are connected in parallel to thecentral processing unit.

Example 17 includes the system of example 11, wherein the write missinformation is first write miss information, further including acontroller to, when a first memory address of the first write missinformation from the first cache storage matches a second memory addressof second write miss information stored in the second portion, merge thefirst write miss information with the second write miss information.

Example 18 includes the system of example 17, wherein the cachecontroller is to merge the first write miss information with the secondwrite miss information by at least one of (a) maintaining first writeinformation of the first write miss information or (b) discarding secondwrite information of the second write miss information when the secondwrite information corresponds to the same one or more bytes as the firstwrite miss information.

Example 19 includes a method comprising receiving a write operation,determining that the write operation produces a miss in a first cachestorage, and in response to the miss in the first cache storage, provingwrite miss information associated with the write operation to a secondcache storage element with a first portion and a second portion forstoring in the second portion, the first portion storing a first set ofdata evicted from the first cache storage.

Example 20 includes the method of example 19, further includingcomparing the second portion of the second cache storage to a threshold,and based on the second portion exceeding the threshold, outputting thewrite miss information to a second cache.

FIG. 4A is an example circuit implementation of the main cache storequeue 212 of FIGS. 2 and/or 3. In FIG. 4A, the main cache store queue212 includes an example latches 402 a, 402 b, 402 c, 402 d, 402 e,example merge circuits 403 a-c, an example arithmetic component 404, anexample atomic compare component 406, an example read-modify-write mergecomponent 408, an example select multiplexer 410, and example ECCgenerator 412, an example arbitration manager 414, an example pendingstore address data store 416, an example priority multiplexer 418, anexample read port 424, and an example write port 426. The example mergecircuits 403 a-d include an example comparator(s) 420, and exampleswitches 422. The example of FIG. 4A illustrates a single pipeline ofthe main cache store queue 212. However, the main storage element 214may be arranged to support more than one independent copy of thepipeline with respect to different banks as indicated by the dashed box400. Accordingly, the pipeline of FIG. 4A may be reproduced multipletimes for different banks, as further described below.

In FIG. 4A, the example latches 402 a, 402 b, 402 c, 402 d, 402 e, areelectronic devices configured to store information (e.g., bytes, bits,etc.) obtained by the main cache store queue 212. The example latches402 a-c pass the write data and information corresponding to whether thewrite data needs to be combined with the read and corrected data out ofthe ECC logic 310 in the arithmetic unit 404, the atomic unit 406,and/or the RMW merge component 408. In the example of FIG. 4A, the latch402 a is communicatively coupled to the cache controller 220 to obtainread, write, and/or modify instructions. Such read, modify, and/or writeinstructions may originate from the CPU 102, and transmitted to thelatch 402 a via the cache controller 220. Latch 402 a is coupled tolatch 402 b, the tag RAM 208, the arbitration manager 414, and thepending store address data store 416 to transmit such read, modify,and/or write instructions to the latch 402 b, the tag RAM 208, thearbitration manager 414, and the pending store address data store 416 inresponse to a subsequent clock cycle of the cache controller 220.

In the example of FIG. 4A, the latch 402 b is coupled to latch 402 a,the pending store address data store 416, latch 402 c, the prioritymultiplexer 418, and the comparator(s) 420 to transmit the obtainedread, modify, and/or write instruction in response to a subsequent clockcycle of the cache controller 220. In this manner, the value obtainedfrom the read, modify, and/or write instruction (e.g., the byte value,the bit value, etc.), propagates through the main cache store queue 212.

The example latch 402 c is coupled to the latch 402 b, the prioritymultiplexer 418, the arithmetic component 404, the atomic comparecomponent 406, and the read-modify-write merge component 408. Thiscoupling enables the latch 402 c to transmit the value obtained from theread, modify, and/or write instruction (e.g., the byte value, the bitvalue, etc.) to the arithmetic component 404, the atomic comparecomponent 406, and/or the read-modify-write merge component 408 inresponse to a subsequent clock cycle of the cache controller 220. Insome examples disclosed herein, latch 402 c may transmit the valueobtained from the read, modify, and/or write instruction (e.g., the bytevalue, the bit value, etc.) to one or more of the arithmetic component404, the atomic compare component 406, and/or the read-modify-writemerge component 408. For example, in the event the cache controller 220transmits an instruction to write a bit into a currently stored word,the latch 402 c may transmit the value obtained from the read, modify,and/or write instruction (e.g., the byte value, the bit value, etc.) tothe read-modify-write merge component 408. In other examples disclosedherein, though the cache controller 220 may transmit an instruction towrite a bit into a currently stored word, the latch 402 c may transmitthe value obtained from the read, modify, and/or write instruction(e.g., the byte value, the bit value, etc.) to the arithmetic component404, the atomic compare component 406, and/or read-modify-write mergecomponent 408.

The example latch 402 d is coupled to the first multiplexer 410, the ECCgenerator 412, and the latch 402 e. This coupling enables the latch 402d to transmit the value obtained from first multiplexer 410 to ECCgenerator 412 and/or the merging circuit 403 a in response to asubsequent clock cycle of the cache controller clock 220.

The example latch 402 e is coupled to priority multiplexer 418 and tothe MUX circuit 314 of FIGS. 3 and/or 4. This coupling enables the latch402 e to transmit the value obtained from the from the prioritymultiplexer 418 to MUX circuit 314 in response to a subsequent clockcycle of the cache controller 220. For example, on a read operation bythe CPU 102 to an address that hits the main storage element 214, aprevious write to the same address could still be inflight (e.g., notcompletely written to the main storage element 214). In such an example,the latch 402 e collects the unwritten data byte and provides it to theMUX 314 which eventually gets sent back to the CPU 102.

The example merging circuit 403 a is coupled to the latch 402 d, themerging circuit 403 b, the arithmetic component 404, the atomic comparecomponent 406, and the read-modify-write merge component 408. Theexample merging circuit 403 b is coupled to the merging circuit 403 a,the priority multiplexer 418, and the merging circuit 403 c. The examplemerging circuit 403 c is coupled to the merging circuit 403 b and thelatch 402 b. The example merging circuits 403 a-c facilitate thecomparison of read operations in different sections of the main cachestore queue 212 to potentially reroute write operations to be mergedwith write operations corresponding to the same memory address location,as further described below. Although the example of FIG. 4A includesthree merging circuits 403 a-c, there may be additional merging circuitsto merge write operations from other sections of the main cache storequeue 212 (e.g., a merging circuit coupling the output of the latch 402d to the output of latch 402 b and/or latch 402 a, etc.). In someexamples, the merging circuits 403 a-c are combined into a singlecircuit that compares the write operations from the different latches402 b-d and reroutes based on matching memory addresses in any two ormore of the different latches 402 b-d.

In the example illustrated in FIG. 4A, the arithmetic component 404 iscoupled to the latch 402 c, the first multiplexer 410, and to the ECClogic 310 to perform arithmetic operations on (e.g., increment,decrement, etc.) data from the main storage 214. Additionally, thearithmetic component 404 performs histogram operations on the datastored in the main storage 214. The example arithmetic component 404 ofthe illustrated example of FIG. 4A is implemented by a logic circuitsuch as, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.Operation of the example arithmetic component 404 is further describedbelow.

In the example illustrated in FIG. 4A, the atomic compare component 406is coupled to the latch 402 c, the first multiplexer 410, and to the ECClogic 310 to compare data at a memory address to a key and, in the eventthe data at the memory address matches the key, replace the data. Theexample atomic compare component 406 the illustrated example of FIG. 4Ais implemented by a logic circuit such as, for example, a hardwareprocessor. However, any other type of circuitry may additionally oralternatively be used such as, for example, one or more analog ordigital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc. Operation of the exampleatomic compare component 406 is further described below.

In the example illustrated in FIG. 4A, the read-modify-write mergecomponent 408 is coupled to the latch 402 c, the first multiplexer 410,and to the ECC logic 310 to facilitate the read, modify, and/or writeinstruction(s) sent by the cache controller 220. For example, theread-modify-write merge component 408 is coupled to the ECC logic 310 toobtain the currently stored word that is to be affected by the read,modify, and/or write instruction(s). In an example write operation, theread-modify-write merge component 408 is configured to update thecurrently stored word obtained from the ECC logic 310 with the newbit(s), byte(s), etc., obtained from the latch 402 c. Additionaldescription of the read-modify-write merge component 408 is describedbelow. The example read-modify-write merge component 408 of theillustrated example of FIG. 4A is implemented by a logic circuit suchas, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.

The example first multiplexer 410 is coupled to the arithmetic component404, the atomic compare component 406, and the read-modify-write mergecomponent 408 to transmit, based on an indication from the cachecontroller 220, the output of either the arithmetic component 404, theatomic compare component 406, or the read-modify-write merge component408 to the latch 402 d. For example, in the event the cache controller220 indicates to perform a write function (e.g., the cache controltransmits a write request to the latch 402 b), an indication is sent bythe cache controller 220 to the first multiplexer 410 to select theinput connected to the read-modify-write merge component 408 to betransmitted to the latch 402 d. The example first multiplexer 410 of theillustrated example of FIG. 4A is implemented by a logic circuit suchas, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.

In the example illustrated in FIG. 4A, the ECC generator 412 is coupledto the latch 402 d and to the merging circuit 403 a to facilitate errordetection and correction in the value (e.g., byte(s), bit(s), etc.)stored in the latch 402 d. For example, the ECC generator 412 isconfigured to regenerate the ECC (E.g., generate error detection code)value which will be stored with the data (e.g., merged word output fromthe read-modify-write merge component 1108). The ECC value is used bythe error detection and correction circuit to determine whether theerror occurred during a read and/or write operation, as furtherdescribed above. The example ECC generator 412 of the illustratedexample of FIG. 4A is implemented by a logic circuit such as, forexample, a hardware processor. However, any other type of circuitry mayadditionally or alternatively be used such as, for example, one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

In FIG. 4A, the example arbitration manager 414 is coupled to the latch402 a, the latch 402 b, the pending store address datastore 416, and themain storage 214 to facilitate the read, modify, and/or writeinstructions obtained from the cache controller 220. For example, in theevent a write instruction is received from the cache controller 220, thearbitration manager 414 is configured to transmit a read instruction ofthe corresponding currently stored word to the main storage 214. Inaddition, the arbitration manager 414 is coupled to the main storage 214to arbitrate between conflicting accesses of the main storage 214. Whenmultiple operations attempt to access the main storage 214 in the samecycle, the arbitration manager 414 may select which operation(s) arepermitted to access the main storage 214 according to a priority scheme.Suitable priority schemes are described in more detail in below;however, in one example, the arbitration prioritizes read operationsover write operations because write data that is in the main cache storequeue 212 is available for use by subsequent operations even before itis written to the main storage 214. Thus, there is minimal performanceimpact in allowing the write data to wait in the main cache store queue212. However, as the main cache store queue 214 fills with write datathat has not yet been written back, the priority of the write operationsmay increase until they are prioritized over competing read operations.

The example arbitration manager 414 of the illustrated example of FIG.4A is implemented by a logic circuit such as, for example, a hardwareprocessor. However, any other type of circuitry may additionally oralternatively be used such as, for example, one or more analog ordigital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

In the example of FIG. 4A, the pending store address data store 416 isconfigured to store the address of the read, modify, and/or writeinstruction obtained from the cache controller 220. In this manner, thepending store address datastore 416 maintains a log of the addressesassociated with each value stored in any of the latches 402 a, 402 b,402 c, 402 d, 402 e, and/or the merging circuits 403 a, 403 b, and/or403 c. The example pending store address datastore 416 of theillustrated example of FIG. 4A may be implemented by any device forstoring data such as, for example, flash memory, magnetic media, opticalmedia, etc. Furthermore, the data stored in the pending store addressdatastore 416 may be in any data format such as, for example, binarydata, comma delimited data, tab delimited data, structured querylanguage (SQL) structures, etc.

The example priority multiplexer 418 is coupled to the latch 402 b, thelatch 402 c, the latch 402 d, and the merging circuit 403 a tofacilitate read operations in the event either of the of the latch 402b, the latch 402 c, the latch 402 d, or the merging circuit 403 a arestoring a value corresponding to a write instruction. For example, thecache controller may initiate the following four write instructionsregarding a four byte word having addresses A3, A2, A1, and A0: writeaddress A0 with the byte 0x11, write address A1 with the byte 0x22,write address A3 with the byte 0x23, and write address A0 with the byte0x44. In such an example, in the event the cache controller 220initiates a read instruction to read the entire four byte word, thepriority multiplexer 418 is configured to obtain the byte value 0x11stored in the merging circuit 403 a, the byte value 0x22 stored in thelatch 402 d, the byte value 0x23 stored in the latch 402 c, and the bytevalue 0x22 stored in the latch 402 b. Additionally, the pending storeaddress data store 416 transmits an instruction to the prioritymultiplexer 418 indicating which address value in is associated with thebyte value stored in the latch 402 b, the latch 402 c, the latch 402 d,and the merging circuit 403 a. In such an example, since the byte valuestored in the latch 402 b is associated with the address A0 and the bytevalue stored in the merging circuit 403 a is also associated with theaddress A0, the priority multiplexer 418 is configured to transmit apacket to the latch 402 e indicating that address A0 is 0x44 (e.g., themost recent write instruction associated with the address A0), addressA1 is 0x22, and address A3 is 0x23.

In this manner, the MUX circuit 314 is configured to update the value ofthe currently stored word with the byte values obtained from thepriority multiplexer 418. Such an operation ensures that a readinstruction transmitted by the main cache store queue 212 probablyindicates the correct word, even though the write instructions may nothave fully propagated through the main cache store queue 212.

An example read path (e.g., the read input to the tag RAM 208) may runin parallel with the main cache store queue 212. Because a readoperation (e.g., a read instruction) may refer to data in a writeoperation (e.g., a write instruction) that may not have completed yet,the main cache store queue 212 may include write forwardingfunctionality that allows the read path to obtain data from the maincache store queue 212 that has not yet been written back to the mainstorage 214. In an example, the main cache store queue 212 includespending store address data store 416 that records the addresses of theoperations at each stage of the main cache store queue 212, a prioritymultiplexer 418 to select data from one of the stages (e.g., latches) ofthe main cache store queue 212 for forwarding, and a MUX circuit 314that selects between the output of the main storage 214 (by way of theerror detection and correction circuit 310) and the forwarded main cachestore queue 212 data from the data priority multiplexer 418.

Alternatively, because a read operation (e.g., a read instruction, aread command, etc.) may refer to victimizing (e.g., evicting) data in awrite operation (e.g., a write instruction, a write command, etc.) thatmay not have completed yet, the main cache store queue 212 includes aread-invalidate functionality that forwards in-flight data (e.g., dataof the store queue 212 not yet stored in the main storage element 214)to the victim storage element 214 and/or the L2 cache 212 andinvalidates the in-flight data remaining in the store queue 212.

The example read port 424 is coupled to the read path and the data store416. The read port 424 may be implemented by an interface thatinterfaces with the main cache controller 222 whenever a read-missoccurs. For example, the read port 424 is utilized to receive victimaddresses and read-invalidate commands from the main cache controller222. The read port 424 is to send the victim addresses to the data store416 to be compared against the pending addresses stored in the datastore 416.

The example write port 426 is coupled to the write path and the latch402 a. The write port 426 may be implemented by an interface thatinterfaces with the main cache controller 222 (e.g., the cachecontroller 220) to obtain a write instruction. For example, the writeport 426 is utilized to receive addresses and values from the cachecontroller 220 to write.

The elements of FIG. 4A are arranged in a manner representing the flowof transaction processing. The temporal elements are represented bystages E1-E5. Each stage represents a discrete period of time, and insome examples each stage represents a clock cycle or an integer numberof clock cycles.

An example flow of a read operation through the main cache store queue212 will now be described. In a first cycle, corresponding to stage E1,the L1 data cache 110 retrieves a record from the tag RAM 208 that isassociated with an address of the read operation to determine whetherthe data is stored in the main storage 214. In a direct mapped example,the L1 data cache 110 need not wait for the tag RAM 208 comparisonbefore requesting data from the main storage 214, and thus, the tag RAM208 comparison between the address of the read operation and the recordof cached addresses may extend into a second or third clock cycle.

In the second cycle, corresponding to stage E2, the L1 data cache 110may request the data and ECC syndrome bits from the main storage 214 ifthe arbitration manager 414 permits. In this cycle, the L1 data cache110 may also determine whether newer data is available in the main cachestore queue 212 by comparing the read address to the pending storeaddress data store 416. If so, the priority multiplexer 418 is set toforward the appropriate data from the main cache store queue 212.

Data and ECC may be provided by the main cache storage 214 in the thirdcycle, corresponding to stage E3. However, this data may or may notcorrespond to the memory address specified by the read operation becausethe L1 data cache 110 may allocate multiple extended memory addresses tothe same entry in the cache's main storage 214. Accordingly, in thethird cycle, the L1 data cache 110 determines whether the provided dataand ECC from the main storage 214 corresponds to the memory address inthe read operation (e.g., a cache hit) based on the comparison of thetag RAM 208 record. In the event of a cache hit, the data and ECC bitsare received by the error detection and correction circuit 310, whichcorrects any errors in the data in a fourth cycle, corresponding tostage E4.

As explained above, newer data that has not yet been written to the mainstorage 214 may be present in the main cache store queue 212, and may beforwarded from the main cache store queue 212 by the prioritymultiplexer 418. If so, the MUX circuit 314 selects the forwarded dataover the corrected data from the main storage 214.

Either the corrected data from the main storage 214 or the forwardeddata from the main cache store queue 212 is provided to the L1 datacache 110 in a fifth cycle, corresponding to stage E5. In this way, thecontroller 220 may provide data with full ECC checking and correction inthe event of a cache hit in about 5 cycles.

In the event that the data and ECC bits are not present in the mainstorage 214 (e.g., a cache miss), the main cache store queue 212 maystall until the data can be retrieved from either the extended memory106 and/or the victim storage 218, at which point the data may bewritten to the main storage and the tag RAM 208 may be updated.

Methods and Apparatus to Facilitate Fully Pipelined Read-Modify-WriteSupport in Level 1 Data Cache Using Store Queue and Data Forwarding

In examples disclosed herein, there are two cache systems operating intandem (e.g., the main storage 214 and the victim cache storage 218). Inexamples disclosed herein, the main storage 214 is a direct mapped cacheelement and the victim cache storage 218 is a fully associative cachestorage. Both the direct mapped main storage 214 and the fullyassociative victim cache storage 218 are protected by an errorcorrecting code (ECC). With this, example applications include reading aline from main storage 214 and/or moving a line from the main storage214. As such, ECC logic would correct the cache line and regenerate theECC syndrome, and then write the line to victim cache storage 218. Suchan application may utilize two additional clock cycles of the CPU (e.g.,one clock cycle for error correction by the ECC logic and another clockcycle for ECC syndrome regeneration). To reduce this latency, examplesdisclosed herein include utilizing the same parity block size betweenthe main storage 214 and the victim cache storage 218. Thus, both themain storage 214 and the victim cache storage 218 calculate and/orotherwise determine parity on a 32-bit boundary. In this manner, the L1cache 110 can move a cache line directly from main storage 214 to thevictim cache storage 218 with less latency.

In examples disclosed herein, the L1 data cache 110 supports a number ofoperations that read data from the cache and make changes to the databefore rewriting it. For example, the L1 data cache 110 may supportread-modify-write operations. A read-modify-write operation readsexisting data and overwrites at least a portion of the data. In ECCembodiments, a read-modify-write operation may be performed when writingless than a full bank width (e.g., when writing less than a 32-bit,4-byte word). The read functionality of the read-modify-write is usedbecause the portion of the data in the bank that will not be overwrittenstill contributes to the ECC syndrome bits.

A read-modify-write operation may be split into a write operation and aread operation, and the main cache store queue 212 may be structuredsuch that the read operation in the read path stays synchronized withthe write operation in the main cache store queue 212. The readoperation and the write operation remain synchronized until theread-modify-write merge component 408 overwrites at least a portion ofthe read data with the write data to produce merged data. The mergeddata is provided to the ECC generator 412 that generates new ECCsyndrome bits for the merged data, and then the merged data and ECCsyndrome bits may be provided to the arbitration manager 414 for storingin the main storage 214.

In an example read-modify-write operation, the cache controller 220 ofFIGS. 2 and/or 3 transmits a write request indicating a subset of bytesof a word, or an entire word (e.g., a first set of data), to be written.In such an example, the write request transmitted by the cachecontroller 220 includes an address value of the byte(s) to be writtenand the data to write to the indicated bytes. For example, the mainstorage 214 of FIGS. 2 and/or 3 may include the four-byte word0x12345678 associated with addresses A3, A2, A1, A0. In such an example,address A3 corresponds to the byte 0x12, address A2 corresponds to thebyte 0x34, address A1 corresponds to the byte 0x56, and address A0corresponds to the byte 0x78 of the stored word. In such an exampleoperation, the cache controller 220 may transmit a write request toreplace address A3 with the byte 0x33, replace address A1 with the byte0x22, and replace address A0 with the byte 0x11 of the currently storedword 12345678. Further in such an example, the first write request toreplace address A3 of the stored word with the byte 0x33 would result inthe stored word becoming 0x33345678, the second write request to replaceaddress A1 of the stored word with the byte 0x22 would result in thestored word becoming 0x33342278, and the third write request to replaceaddress A0 of the stored word with the byte 0x11 would result in thestored word becoming 0x33342211.

To process such a request, the L1 data cache 110 compares an address ofthe read operation to a record of the tag RAM 208, and the L1 data cacherequests the data and ECC syndrome bits from the main storage 214 and/orthe main cache store queue 212. Because the read-modify-write operationwill modify the data, in examples that track MESI (Modified, Exclusive,Shared, and Invalid) states of entries in the main storage 214, a cachehit that is not in either the Modified or Exclusive state may beconsidered a cache miss. When the data is obtained in the proper stateand any errors are corrected, it is provided to the read-modify-writemerge component 408. In this same cycle, the read-modify-write mergecomponent 408 may overwrite at least a portion of the corrected datawith the write data to produce merged data. The ECC generator 412generates new ECC syndrome bits for the merged data.

In examples disclosed herein, the ECC generator 412 operates on wordgranularity. That is, the ECC generator 412 calculates the ECC syndromefor a block of data. In examples disclosed herein, the block of data mayfour bytes (e.g., a word). The main cache store queue 212 processes thewrite instruction by, at a first example cycle (e.g., to compete thefirst write request of replacing address A3 with the byte 0x33), becausethe ECC generator 412 operates on word granularity (e.g., a 4-byte or32-bit word), the cache controller 220 initiates a read request of thecurrently stored byte in address A3 of the currently stored word. Inthis example, the byte and address in the first write request (e.g.,0x33 and A3) is stored in the latch 402 b. In addition, the cachecontroller 220 transmits a read request of the entire currently storedword to the main storage 214. Thus, at the end of the first cycle, aread request of the entire currently stored word is transmitted to themain storage 214 and the byte 0x33 is stored in the first latch 402 b.

At an example second cycle (e.g., to complete the second write requestof replacing address A1 with the byte 0x22) the byte from the firstwrite request is transmitted to the latch 402 c, the entire currentlystored word is transmitted from the main storage 214 to the ECC logic310, and the second write request (e.g., to replace address A1 with thebyte 0x22) is transmitted by the cache controller 220 to be stored inthe latch 402 b. During the second cycle, the read-modify-write mergecomponent 408 obtains the byte stored in the latch 402 c and the entirecurrently stored word transmitted by the ECC logic 310. In this manner,the read-modify-write merge component 408 identifies the address of thebyte in the currently stored word to be updated. Once theread-modify-write merge component 408 identifies and/or otherwiseobtains (a) the value (e.g., byte value, bit value, etc.) of the portionof the currently stored word to be updated from the latch 402 c and the(b) currently stored word from the ECC logic 310, the read-modify-writemerge component 408 writes (e.g., replaces, merges, etc.) the portion ofthe currently stored word with the value of the portion of the currentlystored word obtained from the latch 402 c. For example, theread-modify-write merge component 408 writes the value of the portion ofthe word to an address value corresponding to the portion of the word inthe word. Such an example written portion output by theread-modify-write merge component 408 may be referred to herein as themerged word. In some examples disclosed herein, such a merged word isprovided by the read-modify-write merge component 1108 for writing tothe victim storage 218.

In response, to initiate the write portion of the exampleread-modify-write operation, the select multiplexer 410 transmits themerged word from the read-modify-write merge component 408 to be storedin the latch 402 d. At a subsequent clock cycle, the ECC generator 412obtains the merged word from the latch 402 d and generates thecorresponding ECC syndrome bits. At either the same, or a subsequentclock cycle, the ECC generator 412 transmits the merged word though themerging circuits 403 a, 403 b, and 403 c to be handled by thearbitration manager 414 to be stored in the main storage 214.

However, in such an example described above, because three consecutivewrite instructions were transmitted by the cache controller 220corresponding to the same stored word in the main storage 214, theread-modify-write merge component 408 can merge these three writeinstructions into one transaction when writing the three values of thethree write instructions to the currently stored word. For example,prior to storing the merged word from a first write instruction in themain storage 212, the main storage queue 212 feedbacks (e.g., transmits)the merged word for use in the subsequent second write instruction.

FIG. 4B is an example circuit implementation of example data forwardinglogic 460 implemented in connection with the main cache store queue 212of FIGS. 3A-4A. While FIG. 4B is described as example data forwardinglogic 460 to be implemented in connection with the main cache storequeue 212, in other examples disclosed herein, any of the examplesdescribed in FIG. 4B may be implemented in connection with the victimcache store queue 216.

In the example of FIG. 4B, the example address line 462 (RD_ADDR) iscoupled to the cache controller 220 to obtain an example readinstruction from the CPU 102. In the example of FIG. 4B, such an exampleaddress line 462 obtains the read instruction for the main cache storequeue 212. In this manner, the main cache store queue 212 could forwardany data from in-flight write transactions when executing the CPU 102read instruction. In the main cache store queue 212, an instruction fromthe CPU 102 (e.g., a read instruction and/or otherwise transaction,and/or a write instruction and/or otherwise transaction) includes anaddress, a byte enable (byten) and associated data. The topology of FIG.4B includes example address stores 464 a (e.g., the pending storeaddress data store 416 of FIG. 4), example byten stores 464 b (e.g.,byte enable stores), and example data stores 464 c (e.g., any of thelatches 402 a, 402 b, 402 c, etc.). In FIG. 4B, address addr0 of theaddress stores 464 a corresponds to the oldest read and/or writeinstruction in the main cache store queue 212 and address addr3 of theaddress stores 464 a corresponds to the newest read and/or writeinstruction in the main cache store queue 212.

The incoming address via the address line 462 (e.g., a read instruction)is compared against all the addresses (e.g., addr0, addr1, addr2, andaddr3) in the address stores 464 a by example compare logic 466. Inexamples disclosed herein, the compare logic 466 may compare the addressof the read instruction against any number of entries as addressesaddr0, addr1, addr2, and addr3 may be fully or partially equivalent(e.g., the same). In this manner, the example outputs of the comparelogic 466 are 4-bit signals. Such 4-bit signals are generated based onthe corresponding byte enable signals of the byten stores 464 b. Such4-bit signals may haves any value (e.g., all zeros, all ones, partialzeros and partial ones, etc.).

In example operation, the four addresses of the address stores 464 a mayinclude one or more valid bytes (e.g., bytes that are a logic high). Inexamples disclosed herein, the main cache store queue 212 is 64 bits(e.g., 8 bytes) and, thus, the main cache store queue 212 may perform awrite on any number of bytes, such as, from one to eight.

In response to the compare logic 466 identifying the address of theaddress stores 464 a that are to be included based on the byte enablesin the byten stores 464 b, the example output lines 468 transmit a 8-bitresult for each address in the address stores 464 a. In examplesdisclosed herein, there are four output lines 468 (e.g.,dram_hit_DP0[0][7:0], dram_hit_dp0[1][7:0], dram_hit_dp0[2][7:0] anddram_hit_dp0[3][7:0]). In operation, bits set to a logic high (e.g., 1)in any of the output lines 468 indicate that the corresponding byte ofthe corresponding address of the address stores 464 a has valid data tobe forwarded. For example, if the first output line of the output lines468 includes dram_hit_dp0 [0], the byte value for the corresponding readinstruction may be obtained from any of the addresses in the addressstore 464 a.

The example of FIG. 4B includes example select logic 470 and exampleselect lines 472. In examples disclosed herein, the select lines 472include eight, 2-byte outputs. Accordingly, there is one select signalof the select signals for each of the corresponding byte enables of thebyten stores 464 c. In an example operation, in the event a readinstruction indicates to read multiple addresses having multiple enabledbytes, the example select logic 720 selects the most recent data. Suchan output of the select logic 470 (e.g., the select lines 472) controlexample multiplexers 474 a-474 h (multiplexers 474 e-h not shown),respectively. In the example of FIG. 4B, the multiplexers 474 a-h,include 8 1-byte input terminals. In operation, the multiplexers 474 a-hobtain their respective select line of the select lines 472 whichindicate which byte of each of the data stores 464 c to forward. In thismanner, the main cache store queue 212 can forward data from differentinfight stores (e.g., any of the data stores 464 c) based on addresscomparison (e.g., a comparison performed by the comparators 466), theircorresponding byte enables of the byten stores 464 b, and the order inwhich the main cache store queue 212 was issued a write instruction(e.g., the comparison performed by the select logic 470).

In examples disclosed herein, any of the address line 462, the addressstores 464 a, the byten stores 464 b, the data stores 464 c, the comparelogic 466, the output lines 468, the select logic 470, the select lines472, and/or the multiplexers 474 a-h may be implemented in the victimcache store queue 216. In FIG. 4B, the output terminals of themultiplexers 474 a-h are coupled to an example cache multiplexers 476.In the example of FIG. 4B, cache multiplexer 476 is also coupled tosimilar multiplexers implemented in this manner in association with thevictim cache store queue 216. In operation, the cache multiplexer 476obtains a select signal from the cache controller (e.g., the main cachecontroller 222 or the victim cache controller 224) that transmitted theread instruction. In this manner, the cache multiplexer 476 facilitatesdata forwarding to the CPU 102.

In some examples, the topology of FIG. 4B may correspond to the examplewrite data forwarding component of the main cache store queue 212, thewrite data forwarding component of the victim cache store queue 216, andthe MUX circuits 314, 316. In such an example, the cache multiplexer 476may be implemented by the example MUX circuits 314, 316. Additionally,in such an example, any of the address line 462, the address stores 464a, the byten stores 464 b, the data stores 464 c, the compare logic 466,the output lines 468, the select logic 470, the select lines 472, and/orthe multiplexers 474 a-h may be implemented by the example write dataforwarding component of the main cache store queue 212, and of theaddress line 462, the address stores 464 a, the byten stores 464 b, thedata stores 464 c, the compare logic 466, the output lines 468, theselect logic 470, the select lines 472, and/or the multiplexers 474 a-h,as implemented in association with the victim storage 216, may beimplemented by the example write data forwarding component of the victimcache store queue 216.

In some examples, the topology of FIG. 4B may correspond to the pendingstore address data store 418 and example priority multiplexer 418. Forexample, the address stores 464 a, the byten stores 464 b, and/or thedata stores 464 c may be implemented by the example pending storeaddress data store 416. In a further example, any of the address line462, the compare logic 466, the output lines 468, the select logic 470,the select lines 472, and/or the multiplexers 474 a-h may be implementedby the example priority multiplexer 418.

In examples disclosed herein, the topology of FIG. 4B is utilized foreach bank of the main storage 214 and the victim storage 218. Forexample, if the main storage 214 has 8 banks, the topology of FIG. 4Bwould be replicated 8 times, one for each bank.

Example methods, apparatus, systems, and articles of manufacture tofacilitate fully pipelined read-modify-write support in level 1 datacache using store queue and data forwarding are disclosed herein.Further examples and combinations thereof include the following:

Example 1 includes an apparatus comprising a first storage, a secondstorage, a store queue coupled to the first storage and the secondstorage, the store queue operable to receive a first memory operationspecifying a first set of data, process the first memory operation forstoring the first set of data in at least one of the first storage andthe second storage, receive a second memory operation, and prior tostoring the first set of data in the at least one of the first storageand the second storage, feedback the first set of data for use in thesecond memory operation.

Example 2 includes the apparatus of example 1, wherein the second memoryoperation is a read modify-write operation and specifies a second set ofdata, and the store queue is operable to prior to storing the first setof data in the at least one of the first storage and the second storage,merge the first set of data and the second set of data to produce athird set of data, and provide the third set of data for storing in atleast one of the first storage and the second storage.

Example 3 includes the apparatus of example 2, further includingreceiving a third memory operation indicating to read the third set ofdata.

Example 4 includes the apparatus of example 1, wherein the secondstorage is configured as a victim storage of the first storage.

Example 5 includes the apparatus of example 1, wherein the store queuefurther includes a datastore configured to store a first address valueof the first set of data.

Example 6 includes the apparatus of example 1, wherein the store queuefurther includes an error code correcting generator to generate errordetection code.

Example 7 includes the apparatus of example 6, wherein the error codecorrecting generator is to generate the error detection code in responseto processing the first memory operation.

Example 8 includes a method comprising receiving a first memoryoperation specifying a first set of data, processing the first memoryoperation for storing the first set of data in at least one of a firststorage and a second storage, receiving a second memory operation, andprior to storing the first set of data in the at least one of the firststorage and the second storage, transmitting the first set of data foruse in the second memory operation.

Example 9 includes the method of example 8, wherein the second memoryoperation is a read modify-write operation and specifies a second set ofdata, the method further including prior to storing the first set ofdata in the at least one of the first storage and the second storage,merging the first set of data and the second set of data to produce athird set of data, and providing the third set of data for storing in atleast one of the first storage and the second storage.

Example 10 includes the method of example 9, further including receivinga third memory operation indicating to read the third set of data.

Example 11 includes the method of example 8, wherein the second storageis configured as a victim storage of the first storage.

Example 12 includes the method of example 8, further including storing afirst address value of the first set of data.

Example 13 includes the method of example 8, further includinggenerating error detection code.

Example 14 includes the method of example 13, further includinggenerating the error detection code in response to processing the firstmemory operation.

Example 15 includes a system comprising a central processing unitconfigured to transmit a first memory operation and a second memoryoperation, a first storage coupled to the central processing unit, asecond storage coupled to the central processing unit, a store queuecoupled to the first storage, the second storage, and the centralprocessing unit, the store queue operable to receive the first memoryoperation specifying a first set of data, process the first memoryoperation for storing the first set of data in at least one of the firststorage and the second storage, receive the second memory operation, andprior to storing the first set of data in the at least one of the firststorage and the second storage, feedback the first set of data for usein the second memory operation.

Example 16 includes the system of example 15, wherein the second memoryoperation is a read modify-write operation and specifies a second set ofdata, and the store queue is operable to prior to storing the first setof data in the at least one of the first storage and the second storage,merge the first set of data and the second set of data to produce athird set of data, and provide the third set of data for storing in atleast one of the first storage and the second storage.

Example 17 includes the system of example 16, further includingreceiving a third memory operation indicating to read the third set ofdata.

Example 18 includes the system of example 15, wherein the second storageis configured as a victim storage of the first storage.

Example 19 includes the system of example 15, wherein the store queuefurther includes a datastore configured to store a first address valueof the first set of data.

Example 20 includes the system of example 15, wherein the store queuefurther includes an error code correcting generator to generate errordetection code in response to processing the first memory operation.

Methods and Apparatus to Reduce Read-Modify-Write Cycles for Non-AlignedWrites

When issuing a write instruction to a multi-banked storage, such a writeinstruction may be transmitted with a corresponding read instruction,regardless of the size of the write instruction, in an attempt toexecute a full read-modify-write cycle of such a write instruction. Forexample, in such an application, a write instruction may be obtained bya CPU indicating to write 128 bits across two 64-bit memory banks,starting at address A0 of the first memory bank. In such an example,though the entirety of both the example memory banks are being written,such an application maintains a read instruction to read the datacurrently stored in the two example memory banks. However, such anapproach is inefficient as twice the processing power (e.g., a write anda read instruction) is used. Additionally, such an approach does notprovide any control logic and/or processing circuitry to analyze thewrite instruction.

In the example illustrated in FIG. 4A, the main storage 214 and/or thevictim storage 218 may be multi-banked storages. For example, the mainstorage 214 may include sixteen memory banks (e.g., sixteen sub-RAMs),each 64 bits wide. In such an example, in the event the cache controller220 transmits a write instruction to write all 64 bits of a first bankof the main storage 214 (e.g., write a 64-bit word starting with thefirst address of the first bank), the write instruction can be executedwithout initiating a read instruction. For example, the bank processinglogic 303 may detect that such a write of an entire bank is to beperformed and, thus, indicate to the cache controller 220 to initiatethe read-modify-write operation, negating to transmit the readinstruction.

Similarly, in the event the cache controller 220 transmits a writeinstruction to the write port 426 to write all 128 bits of a first bankand a second bank of the main storage 214 (e.g., a write instructionindicating to write a 128 bit word starting with the first address ofthe first bank and ending with the last address of the second bank), thewrite instruction can be implemented without initiating a readinstruction. For example, the bank processing logic 303 may detect thatsuch a write of the entirety of multiple banks is to be performed and,thus, indicate to the cache controller 220 to initiate theread-modify-write operation, negating to transmit the read instruction.

However, in some examples disclosed herein, the cache controller 220 maytransmit a write instruction to write 130 bits of data (or any writeinstruction indicating to write to a subset of the memory banks). Of the130 bits of data, 64 bits of data may be written to a first bank, 64bits of data may be written to a second bank, and 2 bits of data may bewritten to a third bank of the main storage (e.g., a write instructionindicating to write a 130 bit work starting with the first address ofthe first bank and ending with the second address of the third bank). Insuch an example, the bank processing logic 303 detects that alladdresses of the first bank and the second bank of the main storage 214are to be written entirely and, thus, indicate to the cache controllerto initiate the read-modify-write operations for the first bank and thesecond bank of the main storage, negating to transmit the readinstruction. In such an example, the bank processing logic 303 maydetect (e.g., determine) that a subset of the memory banks of the mainstorage 214 (e.g., the third bank of the memory storage) is to bepartially written (e.g., two addresses of the 64 addresses are to bewritten), and, thus, indicate to the cache controller 220 to initiate afull read-modify-write operation of the third bank of the main storage214. In examples disclosed herein, the bank processing logic 303determines whether to cause a read operation to be performed (e.g.,whether to initiate a full read-modify-write operation) in response tothe write operation based on whether a number of addresses in the subsetof the plurality of memory banks to write satisfies a threshold. Inexamples disclosed herein, the threshold is not satisfied when thenumber of addresses in the subset of the plurality of memory banks isgreater than 0 and/or less than the number of addresses in the memorybank. In this example, the bank processing logic 303 generates anindication to the CPU 102 to execute the write instruction as a fullread-modify-write transaction. In examples disclosed herein, thethreshold is satisfied when the number of addresses in the subset of theplurality of memory banks is equal to the number of addresses in thememory bank. In this example, the bank processing logic 303 generates anindication to the CPU 102 to execute the write instruction as a partialread-modify-write transaction (e.g., negating the read). Exampledescription of a read-modify-write operation is described above.

Example methods, apparatus, systems, and articles of manufacture toreduce read-modify-write cycles for non-aligned writes are disclosedherein. Further examples and combinations thereof include the following:

Example 1 includes an apparatus comprising a memory that includes aplurality of memory banks, an interface configured to be coupled to acentral processing unit, the interface to obtain a write operation fromthe central processing unit, wherein the write operation is to write asubset of the plurality of memory banks, and bank processing logiccoupled to the interface and to the memory, the bank processing logic todetermine the subset of the plurality of memory banks to write based onthe write operation, and determine whether to cause a read operation tobe performed in response to the write operation based on whether anumber of addresses in the subset of the plurality of memory banks towrite satisfies a threshold.

Example 2 includes the apparatus of example 1, wherein the threshold issatisfied when all addresses of the at least one of the number of theplurality of memory banks is included in the write operation.

Example 3 includes the apparatus of example 1, wherein the bankprocessing logic is to when the number of addresses of the at least oneof the number of the plurality of memory banks to write does not satisfythe threshold, generate a second indication to the central processingunit to execute the write operation to the at least one of the number ofthe plurality of memory banks with issuing the read operation.

Example 4 includes the apparatus of example 1, wherein the bankprocessing logic determines the number of the plurality of memory banksto write based on the write operation by determining a total number ofaddresses included in the write operation, and determining the number ofthe plurality of memory banks based on having an address included in thetotal number of addresses.

Example 5 includes the apparatus of example 1, wherein the writeoperation indicates a number of the plurality of memory banks torewrite.

Example 6 includes the apparatus of example 1, wherein the plurality ofmemory banks are sixteen memory banks.

Example 7 includes the apparatus of example 1, wherein the memory is avictim storage.

Example 8 includes a system comprising a central processing unitconfigured to generate a write operation indicating to write to a subsetof a plurality of memory banks, a victim storage including the pluralityof memory banks, and bank processing logic coupled to the centralprocessing unit and to the victim storage, the bank processing logic todetermine the subset of the plurality of memory banks to write based onthe write operation, and determine whether to cause a read operation tobe performed in response to the write operation based on whether anumber of addresses in the subset of the plurality of memory banks towrite satisfies a threshold.

Example 9 includes the system of example 8, wherein the threshold issatisfied when all addresses of the at least one of the number of theplurality of memory banks is included in the write operation.

Example 10 includes the system of example 8, wherein the bank processinglogic is to when the number of addresses of the at least one of thenumber of the plurality of memory banks to write does not satisfy thethreshold, generate a second indication to the central processing unitto execute the write operation to the at least one of the number of theplurality of memory banks with issuing the read operation.

Example 11 includes the system of example 10, wherein the centralprocessing unit is further to generate a read-modify-write operation tobe executed by the at least one of the number of the plurality of memorybanks in response to the second indication.

Example 12 includes the system of example 8, wherein the bank processinglogic determines the number of the plurality of memory banks to writebased on the write operation by determining a total number of addressesincluded in the write operation, and determining the number of theplurality of memory banks based on having an address included in thetotal number of addresses.

Example 13 includes a method comprising determining a subset of aplurality of memory banks of a memory to write based on a writeoperation, and determine whether to cause a read operation to beperformed in response to the write operation based on whether a numberof addresses in the subset of the plurality of memory banks to writesatisfies a threshold.

Example 14 includes the method of example 13, further includingtransmitting an indication to a central processing unit in response tothe threshold being satisfied.

Example 15 includes the method of example 13, wherein the threshold issatisfied when all addresses of the at least one of the number of theplurality of memory banks is included in the write operation.

Example 16 includes the method of example 13, further including when thenumber of addresses of the at least one of the number of the pluralityof memory banks to write does not satisfy the threshold, generating asecond indication to execute the write operation to the at least one ofthe number of the plurality of memory banks with issuing the readoperation.

Example 17 includes the method of example 13, wherein determining thenumber of the plurality of memory banks to write is performed bydetermining a total number of addresses included in the write operation,and determining the number of the plurality of memory banks based onhaving an address included in the total number of addresses.

Example 18 includes the method of example 13, wherein the writeoperation indicates a number of the plurality of memory banks torewrite.

Example 19 includes the method of example 14, further includingobtaining the write operation from the central processing unit, thewrite operation indicating the number of the plurality of memory banksto write.

Example 20 includes the method of example 14, wherein the memory is avictim storage.

Aggressive Write Merging to Reduce Bank Pressure

In the example of FIG. 4A, the example main cache store queue 212 storesa number of write operations at different sections of the main cachestore queue 212 (e.g., at the example latches 402 a-e). For example,when the CPU 102 transmits three separate write operations in a row, thefirst write operation that the CPU 102 provided is stored at the firstlatch 402 b and moved to the second latch 402 c when the secondoperation is received at the first latch 402 b. Accordingly, after thethree write operations are received, the first latch 402 b will storeand/or output the last write operation with respect to time (e.g., whichis last to be stored in the main storage 214), the second latch 402 cwill have the second write operation (e.g., which is second to be storedin the main storage 214), and the third latch 402 d will have the firstwrite operation (e.g., which was the first to be stored in the examplemain storage 214). Whenever data in the main cache store queue 212 isnext to be stored in the main storage 214, the example arbitrationmanager 414 reserves a cycle for the data to be written into the examplemain storage 214. Accordingly, during the reserved cycle, the mainstorage 214 may not be available to perform read operations. However, ifthe data operations stored in two or more of the latches 402 b, 402 c,402 d correspond to the same memory address, the data can be merged inorder to write the data into the memory address of the main storage 214once, instead of two or three times. For example, if the write operationstored in the latch 402 d corresponds to writing a byte of the memoryaddress and the write operation stored in the latch 402 c corresponds towriting the same byte to the memory address, the second write willoverwrite the first write.

Instead of reserving a cycle to write the first byte into the mainstorage 214, which will be overwritten in a subsequent cycle, the maincache store queue 212 merges the two writes into one write, so that onlyone cycle is used to write the second transaction (e.g., to avoidreserving a cycle for the first write). Such an aggressive merge reducesthe number of cycles reserved for write operations. In this manner, themain storage 214 will have extra cycles to perform read operations,thereby decreasing the latency of the overall systems.

To enable an aggressive merge of write operations to the same memoryaddress, the output of the example latches 402 b-402 d are coupled tothe example merging circuits 403 a-403 c. For example, the output of thethird latch 402 d may be coupled to the merging circuit 403 a, theoutput of the second latch 402 c may be coupled to the merging circuit403 b, and the output of the first latch 402 b may couple to the mergingcircuit 403 c. The output of the merging circuit 403 a may additionallybe coupled to the output of the second latch 402 c and the mergingcircuit 403 b, the merging circuit 403 b may be coupled to the mergingcircuit 403 c, and the merging circuit 403 c may be coupled to the inputof the first latch 402 b. Additionally or alternatively, there may beadditional comparator circuits that compare outputs of a different setof latches (e.g., a comparator circuit to compare the output of latch402 b with the output of latch 402 d). The example merging circuits 403a-c include example comparator(s) 420 and example switches 422.

The comparator(s) 420 compare the memory address locations for eachwrite operation that is stored in the respective laches 402 b-402 d todetermine whether any of the write operations in the example store queuecorrespond to the same memory address. The example comparator 420 may beone comparator to compare all the write operations of the latches 402b-402 d or may be separate comparators 420, to compare two of thelatches 402 b-d (e.g., a first comparator to the memory address of latch402 b to the memory address of latch 402 c, a second comparator to thememory address of 402 b to the memory address of latch 402 d, etc.). Thecomparator(s) 420 output the results of the comparisons (e.g., with oneor more signals corresponding to the one or more comparisons) to theexample switch(es) 422 and/or the arbitration manager 414. If theexample arbitration manager 414 receives a signal indicative of a match,the arbitration manager 414 will not reserve the cycle for a first writeoperation while the first write operation is merged with a second writeoperation to the same memory location (e.g., to free up cycles for othercache operations).

The example switch(es) 422 reroute the write operations in the examplelatches 402 b-402 d based on the comparison. For example, if the memoryaddress of the write operation stored in the example latch 402 d is thesame as the memory address stored in the latch 402 c, the exampleswitch(es) 422 enable and/or disable to reroute the output of the latch402 d to latch 402 c, instead of routing to the example arbitrationmanager 414. In this manner, the two write operations are combined andwritten into the main storage 214 in a subsequent cycle as a singlewrite operation instead of two write operations. The switch(es) 422 maybe electrical switches, transistors (e.g., MOSFETS), demultiplexers,and/or any other component that can reroute a signal in a circuit.

When a MUX of one of the merging circuit 403 a-c receives a reroutedwrite operation, the MUX performs a merging protocol for the one or morererouted write operations that prioritizes the newest write operation.For example, if the comparator(s) 420 determines that the writeoperation stored in the example latch 402 c corresponds to the samememory address as the write operation stored in the example latch 402 d,the MUX of the comparator(s) 420 merge the data (as further described inconjunction with FIG. 4D) and the switches(es) 422 reroute the mergedwrite operation stored in the example latch 402 d to the latch 402 c. Insuch an example, if the write operation in the example latch 402 ccorresponds to writing data to byte0 and byte2 of the memory address andthe write operation from the latch 404 d corresponds to writing data tobyte0 and byte1, the example merging circuit 403 a merges the two writeoperations to keep the writing data stored in latch 402 c (e.g., thewrite to byte0 and byte2) and include the write data from latch 402 dthat doesn't overlap (e.g., byte2). In this example, the merging circuit403 a discards the write data of byte 0 from the latch 404 d as part ofthe merging operation because the data to be written at byte 0 from thelatch 404 d will be overwritten by the write instructions of the latch402 c. Accordingly, in the above example, the merged data corresponds tothe write data for byte0 from latch 402 c, the write data for byte1 fromlatch 404 d, and the write data for byte2 from the latch 402 c. When asubsequent write operation is added to the main cache store queue 212,the merged write data from the latch 402 c may be manipulated (e.g., viaone of the example blocks 404, 406, 408) and/or pushed to the next latch402 d to be stored in the example main storage 214 during a subsequentcycle. An example hardware implementation of the merging protocol isfurther described below in conjunction with FIG. 4D.

FIG. 4D illustrates a hardware implementation of the merging circuit 402c of FIG. 4A and/or 1102 c of FIG. 11A (e.g., to merge data from thelatch 402 d to the latch 402 c). Similar hardware setups can beimplemented to merge data between any two latches. The example of FIG.4D includes the example latches (e.g., stores) 402 b-402 d and hardwarecomponents for the comparator 420 and the switch 422 of FIG. 4A. Theexample comparator circuit 420 includes comparators and/or logic gates480 a-480 f and the switch circuit 422 includes an OR gate 482 and a MUX484. Although described in conjunction with FIG. 4A, if described inconjunction with the victim cache store queue 216 of FIG. 11A, thelatches 1102 a-d, example comparator 1120 and example switch 322 of FIG.11A could be used.

In the example of FIG. 4D, the example latch 402 d outputs the storeddata to the example storage (e.g., the main storage 214 or the victimstorage 218 via the arbitration manager 414, 1114), which locks its bankfor a first cycle. FIG. 4D illustrates the write-merge locking old datain the bank of the storage when the old data is preceded by anotherstore/latch including new write data to the same address. Although theexample of FIG. 4C illustrates a merge between the example latch 402 dand the example latch 402 c, a similar structure may be used to mergedata between any of the latches 402 a-402 d. For example, if the addressof data at the latch 402 d matches with the address of the data at thelatch 402 b, then the latch 402 can merge its data with the data atlatch 402 b. Additionally, the data at three or more latches may bemerged into a single latch if the data at the three or more latchescorrespond to the same address. As described above, if the data at aparticular latch is merged with data and a prior latch, the data at theparticular latch is invalid (e.g., by setting a bit to a valuecorresponding to invalided) or discarded so that the arbitration is notperformed for that data to be locked in a bank in the storage.

In operation, the example comparator 480 b compares the address of thedata at latch 402 d is compared to the address of the data at latch 403c. The output of the comparator 480 b is valid only if both the latches402 c and 402 d include a bit that is set to valid. Accordingly, theexample comparator 480 a compares the valid bits from the latches 402 c,402 d to ensure that the bits are both valid. In this manner, theexample comparator 480 d only outputs a value (e.g., ‘1’) when theaddress at latch 402 c and the address at latch 402 d are the same andthe valid bits of both latches 402 c, 402 d are valid. Otherwise, theexample comparator 480 d outputs a second value (‘0’). The output of thecomparator 480 d is input to the select line of the MUX 484 of theswitch 422. Thus, if the addresses of the latches 402 c, 402 d are thesame and value, the comparator 480 d will control the MUX 484 of theswitch 422 to output merged data (e.g., from the OR gate 482 of theswitch 422).

The example ADD gate 480 c performs a logic AND function with the bytenof latch 402 d and not of the byten of latch 402 c (e.g., using a NOTgate). The output of the example ADD gate 480 c ensures that if there isa byte being written by both the latch 402 c and 402 d, then the latch402 c is held and the latch 402 d is ignored because the latch 402 c hasthe most recent store issued by the CPU 102. Accordingly, the examplecomparator 480 f only outputs the most recent stored issued by the CPU102 for an address in the store queue. The output of the comparator 480f corresponds to dram_mrg_data_sel[7:0], which is the signal used toselect final merged data between the logic gate 402 d and logic gate 402c on a byte by byte basis. Similar merge logic exists on merging thebyten of the latch 402 c and the latch 402 d. The signal marked as (1)is used to selected between store_byten or (store3_byten merged withstore_4_byten), as described above.

Example methods, apparatus, systems, and articles of manufacture tofacilitate aggressive write merging to reduce bank pressure aredisclosed herein. Further examples and combinations thereof include thefollowing: Example 1 includes an apparatus comprising a first cachestorage, a second cache storage, a store queue coupled to at least oneof the first cache storage and the second cache storage and operable toreceive a first memory operation, process the first memory operation forstoring the first set of data in at least one of the first cache storageand the second cache storage, receive a second memory operation, andprior to storing the first set of data in the at least one of the firstcache storage and the second cache storage, merge the first memoryoperation and the second memory operation.

Example 2 includes the apparatus of example 1, wherein the first memoryoperation specifies a first set of data, the second memory operationspecifies a second set of data, and the store queue is operable to priorto storing the first set of data in the at least one of the first cachestorage and the second cache storage, merge the first set of data andthe second set of data to produce a third set of data, and provide thethird set of data for storing in at least one of the first cache storageand the second cache storage.

Example 3 includes the apparatus of example 2, wherein the store queueis to store the third set of data in the at least one of the first cachestorage or the second cache storage in one cycle.

Example 4 includes the apparatus of example 1, wherein the store queueis operable to merge the first memory operation and the second memoryoperation by cancelling a part of the first memory operation.

Example 5 includes the apparatus of example 4, wherein the part of thefirst memory operation are bytes that the second memory operation is towrite to.

Example 6 includes the apparatus of example 4, wherein the part is afirst part, the store queue operable to merge the first memory operationand the second memory operation by maintaining a second part of thefirst memory operation.

Example 7 includes the apparatus of example 6, wherein the second partof the first memory operation are bytes that the second memory operationis not to write to.

Example 8 includes the apparatus of example 1, wherein the first cachestorage is a main cache storage and the second cache storage is a victimcache storage.

Example 9 includes a system comprising a central processing unit coupledin parallel to a first cache storage and a second cache storage, a storequeue coupled to at least one of the first cache storage and the secondcache storage and operable to process a first memory operation from thecentral processing unit, the first memory operation for storing thefirst set of data in at least one of the first cache storage and thesecond cache storage, prior to storing the first set of data in the atleast one of the first cache storage and the second cache storage, mergethe first memory operation and a second memory operation correspondingto a same memory address.

Example 10 includes the system of example 9, wherein the first memoryoperation specifies a first set of data, the second memory operationspecifies a second set of data, and the store queue is operable to priorto storing the first set of data in the at least one of the first cachestorage and the second cache storage, merge the first set of data andthe second set of data to produce a third set of data, and provide thethird set of data for storing in at least one of the first cache storageand the second cache storage.

Example 11 includes the apparatus of example 10, further including astore queue to store the third set of data in the at least one of thefirst cache storage or the second cache storage in one cycle.

Example 12 includes the system of example 9, wherein the store queue isoperable to merge the first memory operation and the second memoryoperation by cancelling a part of the first memory operation.

Example 13 includes the system of example 12, wherein the part of thefirst memory operation are bytes that the second memory operation is towrite to.

Example 14 includes the system of example 12, wherein the part is afirst part, the store queue operable to merge the first memory operationand the second memory operation by maintaining a second part of thefirst memory operation.

Example 15 includes the system of example 14, wherein the second part ofthe first memory operation are bytes that the second memory operation isnot to write to.

Example 16 includes the system of example 9, wherein the first cachestorage is a main cache storage and the second cache storage is a victimcache storage.

Example 17 includes a method comprising obtaining a first memoryoperation, processing, by executing an instruction with a processor, thefirst memory operation for storing a first set of data in at least oneof a first cache storage and a second cache storage, obtaining a secondmemory operation, and prior to storing the first set of data in the atleast one of the first cache storage and the second cache storage,merging, by executing an instruction with the processor, the firstmemory operation and the second memory operation.

Example 18 includes the method of example 17, wherein the first memoryoperation corresponds to a first set of data and the second memoryoperation corresponds to a second set of data, further including priorto storing the first set of data in the at least one of the first cachestorage and the second cache storage, merging the first set of data andthe second set of data to produce a third set of data, and providing thethird set of data for storing in at least one of the first cache storageand the second cache storage.

Example 19 includes the method of example 18, further including storingthe third set of data in the at least one of the first cache storage orthe second cache storage in one cycle.

Example 20 includes the method of example 17, further including mergingthe first memory operation and the second memory operation by cancellinga part of the first memory operation.

Optimized Atomic Operations and Histogram Operations Support in L1 Cache

Atomic operations are further examples of multi-part memory operations.For example, an atomic compare and swap operation manipulates a valuestored at a memory location based on the results of a comparison of theexisting value stored at the memory location. For example, the CPU 102may want to replace the data stored in the L1 cache 110 with a new valueif the existing value stored in the L1 cache 110 matches a specificvalue.

In some example systems, when a CPU wanted to perform an atomicoperation, the CPU sent a read operation to a memory address, performedthe manipulation on the read data, and then executed a write operationto the same memory address to store the manipulated data. Additionally,in such example systems, the L1 cache paused, rejected, blocked, and/orhalted any transactions from other devices (e.g., other cores of theCPU, higher level cache, the extended memory, etc.) until the atomicoperation was complete (e.g., to avoid manipulation of the memoryaddress corresponding to the atomic operation during the atomicoperation). Accordingly, such example techniques required lots of efforton behalf of the CPU and lots of reserved cycles that increase latency.

In the example of FIG. 4A, the example main cache store queue 212handles atomic operations in conjunction with the read modify writestructure. In this manner, the example CPU 102 can send a single atomicoperation to the L1 cache 110, and the main cache store queue 212handles the atomic data manipulation and writing operation. Accordingly,the CPU 102 utilizes a single cycle to execute an atomic operation andcan use the other cycles (e.g., used in some example atomic protocols)to perform other functions, thereby reducing the latency of the overallcomputing system 100.

In operation, when the CPU 102 transmits an atomic operation and/or anatomic compare and swap operation to increment and/or swap the data at amemory address by a value of 1, for example, the atomic instruction isreceived by the latch 402 a and the tag RAM 208 verifies whether thememory address is stored in the example main storage 214. If the memoryaddress is stored in the example main storage 214, the tag RAM 208instructs the example main storage 214 to output the data at the memoryaddress while the atomic instructions are passed to the example latch402 b. While the main storage 214 outputs the data to the latch 322 a,the example latch 402 b outputs the atomic operation to the latch 402 c.At this point the ECC logic 310 performs error detection and/orcorrection protocol as described above, and the data from the memoryaddress location is forwarded to the example arithmetic component 404(e.g., for atomic operations) or the atomic compare component 406 (e.g.,for the atomic compare and swap operations). The arithmetic component404 obtains the atomic operation (e.g., including data identifying howto manipulate the data) and/or the atomic compare and swap 406 obtainsthe atomic compare and swap operation (e.g., including a key and data tobe written if the key matches read data) from the latch 402 c andobtains the data from the corresponding memory address from the outputof the ECC logic 310. The arithmetic component 404 performs themanipulation to the data (e.g., increment the data by 1) and/or theatomic compare component 406 may perform the swap (replaces the data ifthe read data matches a key, etc.) and outputs the incremented and/orswapped-in data for the corresponding memory address (e.g., the atomicresult) to the example latch 402 d via the example MUX 410. (e.g., whichis enabled via the cache controller 220). The latch 402 d outputs thenew data corresponding to the memory address to the ECC generator 412 togenerate the ECC bit and the arbitration manager 414 writes the new data(e.g., the atomic result and/or atomic compare and swap result) to thememory address in conjunction with the ECC bit in the example mainstorage 214. Additionally or alternatively, the corrected value out ofthe EDD logic 412 is returned to the CPU 102. Thus, the atomic operationis performed with only one instruction from the CPU 102.

The atomic compare component 406 and/or the arithmetic component 404have several inputs. For example, the atomic component 406 receives(e.g., obtains) the type of atomic operation to perform (e.g. atomiccompare and swap, or atomic swap), the new data to swap in, the ECCcorrected data read out the of the cache 310, and the size of the sizeof the data to be manipulated during the atomic operation (e.g., 32-bitor 64-bit), In the example circuit implementation 450 of FIG. 4B, theatomic compare component 406 receives an atomic compare and swapoperation and the arithmetic component 404 receives an atomic operation.The atomic compare component 406 compares the comparison value (e.g., akey) provided by the CPU 102 against the ECC data 310. On a match, thenew data is swapped in place of the old data (e.g. ECC data 310) andoutput to the MUX 410. The size of the new data swapped-in is determinedby cas_acc_sz input (e.g. 32-bit or 64-bit). In the example circuitimplementation 450 of FIG. 4C, the atomic compare component 406 may alsoreceive an atomic swap operation. The atomic compare component 406 willswap-in the new data replacing the ECC data 310 regardless of thecomparison result and output the new value to the mux 410 and the olddata from the address is read from the main storage 214 and is providedback to the CPU 102. The size of the new data swapped-in is determinedby cas_acc_sz input (e.g. 32-bit or 64-bit). In the example circuitimplementation 450 of FIG. 4C, the arithmetic component 404 may alsoreceive an atomic operation. The arithmetic component 404 willmanipulate the ECC data 310 and store the manipulated data in the mainstorage element 214. The size of the new data swapped-in is determinedby cas_acc_sz input (e.g. 32-bit or 64-bit). Although the examplecircuit 450 of FIG. 4C is described above in conjunction with the mainstore queue, the circuit 450 can be described in conjunction with avictim store queue as further described below in conjunction with FIG.11A.

FIG. 4C illustrates an example circuit diagram of parts of the maincache store queue 212 of FIG. 4A and/or parts of the victim cache storequeue 216 of FIG. 11A. FIG. 4C illustrates a detailed circuit diagram ofthe arithmetic unit 404, 1104.

The arithmetic unit 404 may be used for other types of memorytransactions such as histogram operations. A histogram operationretrieves a value stored in memory that may represent a bin of ahistogram, the histogram operation then modifies the values beforestoring it back to the same memory address or an alternative address. Inan example, a first data set contains the values [0, 0, 2, 0, 0, 3], anda second data set contains bins representing the number of occurrencesof respective values within the first data set. In some example systemsthat lack an arithmetic unit 404, to perform a histogram function, theCPU reads each in the first data set and increments the second data setfor each value. For example, to determine how many 0s are stored in a 10byte data set, the CPU may perform 10 reads. Then to determine how many1s are in the same data set, the CPU will perform an additional 10reads. Thus, to perform a histogram operation, such systems may need toperform (N)(M) reads, where N is the size of the section of memory(e.g., 10 bytes) being read and M is the number of values that could bestore in each byte. Like an atomic operation, the L1 SRAM may have toblock, pause, halt, discard, etc. all other read and/or write operationsuntil the histogram operation is complete. In contrast, the arithmeticunit 404 may be used to perform the same operation with a singletransaction from the CPU.

The arithmetic unit 404, 1104 has several inputs including the type ofhistogram (e.g., weighted or increment, signed or not signed), histogramsize (e.g., byte, halfword, or word), histogram weight (e.g., signedweights to be added per selected bins for weighted histograms, weightequal to one for normal histogram), histogram sign (e.g., existing bigsigned or not), and histogram saturate enable.

Component 451 of FIG. 4C selects a bin read out of the ECC component 310for the bank illustrated in FIG. 4C. Component 452 selects the weight tobe added to the bin from the vector of weights provided by the CPU 102.Cnt_value is the sum of the bin value from component 451 and the weightprovided by the CPU 102. Component 453, component 454 and component 458are used as part of the saturation circuit. Component 453 receives thehistogram size (byte, halfword, or word) and the count value (the sum ofthe outputs of components 451, 452) and determines if a signed bin willsaturate. Component 454 receives the histogram size (byte, halfword, orword) and the count value (the sum of the outputs of components 451,452) and determines if a unsigned bin will saturate. The outputs ofcomponents 453 and 454 are sent to a MUX which selects whether to usethe signed saturate value or the unsigned saturate values based on thekind of bin selected (e.g. signed or unsigned). Component 458 receivesthe output of the MUX, the histogram saturate enable, the type ofhistogram (e.g. signed or not signed), the sign bit of the bin, and thesign bit of the weight and outputs an updated cnt_value adjusted for theselected saturation kind (e.g., based on the above Table 1). Components455, 456, 457 are used to position the resultant cnt_value and byteenables in the correct bit positions for writing the new data bank tothe correct bin.

In the example of FIG. 4A, the CPU 102 instructs the main storage 214 toperform the histogram operation. Thereby changing the number of cyclesthat the CPU 102 has to reserve for the operation from (N)(M) to 1.Additionally, because the atomic operation protocol is alreadyimplemented in the store queue, the histogram operation can be performedusing the arithmetic component 404 by performing N reads for the N sizeof the memory and incrementing a count for each value in the examplemain cache store queue 212, thereby reducing the number or readoperation from (N)(M) operations to N operations.

In operation, when the CPU 102 transmits a histogram operationcorresponding to a section (e.g., a SRAM line) of the main storage 214,the histogram operation is stored in the example latch 402 a while thetag RAM 208 verifies whether the memory address corresponding to thehistogram operation is available in the main storage 214. The examplecache controller 220 facilitates the read operation for each byte of thesection identified in the histogram operation (e.g., where histogrambins are accessed in parallel by reading up to 128 Bytes at the sametime). If available, the tag RAM 208 instructs the main storage 214 tooutput the data at a first byte of the section of the main storage 214while the histogram operation is output by the example latch 402 a tothe example latch 402 b. When the example main storage 214 outputs thedata that has been read from the memory address to the example latch 322a, the latch 402 b outputs the histogram operation to the example latch402 c. After the ECC logic 310 performs the error detection andcorrection functionality, the data read at the byte is sent to theexample arithmetic component 404.

After receiving the read value from the ECC logic 310 and the histograminstructions from the latch 402 c, the arithmetic component 404initiates data representative of the histogram. For example, thearithmetic component 404 may initiate a vector (e.g., representing ahistogram) with an initial value (e.g., zero) for each possible valuethat could be stored in the bytes of the main storage. The arithmeticcomponent 404 increments the value of the vector based on output by theECC logic 310 (e.g., the read byte). For example, if the read value ofthe byte is 0, the arithmetic component 404 increments the valuecorresponding to 0 in the vector.

Because each vector is incremented in parallel, the resulting vectorcorresponds to a histogram of the values that were read in thecorresponding sections of SRAM in parallel. Because a value of thehistogram is incremented for each bit, the resulting vector is ahistogram of the values stored in the section of memory identified inthe histogram operation from the CPU 102. In some examples, thearithmetic component 404 may increment in parallel by some weightedvalue (e.g., 1.5). When complete, the example histogram is input to theexample MUX 418 (e.g., controlled by the example pending store addresstable 416) to be input to the MUX 314 via the example latch 402 e. Oncethe operation is complete, the example cache controller 220 controls theMUX 314 to output the final histogram vector to the example CPUinterface 202 via the example latch 322 b, thereby ending the histogramoperation.

In some examples, the L1 cache 110 supports functionality where ahistogram bin can saturate after the histogram bin includes more than athreshold limit of the bin size (e.g., a byte, a halfword, a word,etc.). The below Table 1 illustrates an example of saturation values.Using this functionality, the histogram bin values will not roll overonce they reach the maximum value.

TABLE 1 Histogram Saturation Values Saturate Min Saturate Max UnsaturateMin Unsaturate Max Byte Signed 0x80 0x7F 0x80 0x7F Byte Unsigned 0x00xFF 0x0 0xFF HalfWord Signed 0x8000 0x7FFF 0x8000 0x7FFF HalfWordUnsigned 0x0 0xFFFF 0x0 0xFF Word Signed 0x8000_0000 0x7FFF_FFFF0x8000_0000 0x7FFF_FFFF

Example methods, apparatus, systems, and articles of manufacture tofacilitate optimized atomic and histogram operations are disclosedherein. Further examples and combinations thereof include the following:Example 1 includes a system comprising a cache storage coupled to anarithmetic component, and a cache controller coupled to the cachestorage, wherein the cache controller is operable to receive a memoryoperation that specifies a set of data, retrieve the set of data fromthe cache storage, utilize the arithmetic component to determine a setof counts of respective values in the set of data, generate a vectorrepresenting the set of counts, and provide the vector.

Example 2 includes the system of example 1, wherein the cache controlleris operable to provide the vector for storing in the cache storage.

Example 3 includes the system of example 1, wherein the cache controlleris operable to provide the vector to a processor.

Example 4 includes the system of example 1, further including a storequeue coupled to the cache controller, the store queue including thearithmetic component.

Example 5 includes the system of example 1, wherein the cache storage isat least one of a main cache storage or a victim cache storage.

Example 6 includes the system of example 1, wherein the arithmeticcomponent is to obtain (a) the set of data from the cache storage via anerror detection and correction circuit and (b) the memory operation froma central processing unit via a latch.

Example 7 includes the system of example 1, wherein the cache controlleris operable to provide the vector to a central processing unit based ona single instruction from the central processing unit at a single cycle.

Example 8 includes a system comprising a cache storage, and a cachecontroller coupled to the cache storage and an arithmetic component,wherein the cache controller is operable to receive a memory operationspecifying a first set of data and an arithmetic operation, retrieve thefirst set of data from the cache storage, utilize the arithmeticcomponent to perform the arithmetic operation on the first set of datato produce a second set of data, and provide the second set of data.

Example 9 includes the system of example 8, wherein the cache controlleris operable to provide the second set of data for storing in the cachestorage.

Example 10 includes the system of example 8, wherein the cachecontroller is operable to provide the second set of data to a processor.

Example 11 includes the system of example 8, further including a storequeue coupled to the cache controller, the store queue including thearithmetic component.

Example 12 includes the system of example 8, wherein the cache storageis at least one of a main cache storage or a victim cache storage.

Example 13 includes the system of example 8, wherein the arithmeticcomponent is to obtain (a) the first set of data from the cache storagevia an error detection and correction circuit and (b) the memoryoperation from a central processing unit via a latch.

Example 14 includes the system of example 8, wherein the cachecontroller is operable to provide the second set of data to a centralprocessing unit based on a single instruction from the centralprocessing unit at a single cycle.

Example 15 includes a method comprising obtaining a memory operationthat specifies a set of data, obtaining the set of data from a cachestorage, determining a set of counts of respective values in the set ofdata, generating a vector representing the set of counts, and providingthe vector.

Example 16 includes the method of example 15, wherein the vector isprovided to the cache storage.

Example 17 includes the method of example 15, wherein the vector isprovided to a processor.

Example 18 includes the method of example 15, wherein the cache storageis at least one of a main cache storage or a victim cache storage.

Example 19 includes the method of example 15, further includingobtaining (a) the set of data from the cache storage via an errordetection and correction circuit and (b) the memory operation from acentral processing unit via a latch.

Example 20 includes the method of example 15, wherein the providing thevector to a central processing unit is based on a single instructionfrom the central processing unit at a single cycle.

Atomic Compare and Swap Support in L1 Cache for Coherent System

If data from an address is stored in the L1 cache 110, data for the sameaddress may also be cached in other caches (e.g., L2 cache 112, and/orL3 cache 114). Accordingly, the memory address needs to be trackedand/or monitored to ensure that any changes to the data in one cache isidentified, tracked, and/or reflected to the other caches (e.g., L2cache 112 and L3 cache 114). As described above in conjunction withFIGS. 3A-3D, the example MESI RAM 300 tracks the state of the datastored in the main storage 214 to be able to avoid issues withmismatched data in different caches that correspond to the same memoryaddress. For example, if the CPU 102 transmits a read operation, theexample MESI RAM 300 changes the state of the memory address to shared,because the data in the memory address will not be manipulated. If theCPU 102 transmits a write operation, the example MESI RAM 300 changesthe state of the memory address to exclusive, because the data in thememory address will be manipulated and the main storage 214 needs writepermission for the address. After the data in the memory address iswritten to the main storage 214, the MESI RAM 300 updates the state ofthe memory address to modified (e.g., indicating that the memory addresshas been modified).

As described above, during atomic and/or histogram protocols, the datafrom a memory address is read from the main storage 214 and provided tothe main cache store queue 212 to be updated (e.g., incremented) andwritten back into the main storage 214. However, if the MESI RAM 300 hasidentified the state of the corresponding memory address as in sharedstate, the write operation of the atomic protocol may cause problemswith other level caches (e.g., because the write will cause a mismatchof data in different caches).

To avoid such data mismatches during atomic operations (e.g., includingatomic compare and swap), the example cache controller 220 marks cachehits that correspond to a shared state as a cache miss. In this manner,the cache controller 220 can instruct the L2 interface 228 to send thecache miss to the higher level cache with an exclusive state request. Inthis manner, the higher level cache can grant the exclusive state to theL1 cache 110 and the L1 cache 110 can perform the read and writeoperation as part of the atomic operation in response to receiving thegranted exclusive state.

After the cache miss with exclusive request is sent to the higher levelcache and the higher level cache responds with the write data and theexclusive response, the example atomic operation logic 406 will instructthe MESI RAM 300 to tag the data as modified. The received data from theL2 cache 112 is transmitted into the main cache store queue 212 to bestored in the main storage 214. Because the operation was an atomicoperation (e.g., a regular atomic operation or an atomic compare andswap) or a histogram protocol, the data from the higher level cache ismanipulated by the example arithmetic component 404 and/or the exampleatomic compare component 406 for the manipulation and stored in theexample main storage 215 via the example ECC generator 412 and theexample arbitration manager 414.

Example methods, apparatus, systems, and articles of manufacture tofacilitate an atomic compare and swap are disclosed herein. Furtherexamples and combinations thereof include the following: Example 1includes a system comprising a cache storage, a cache controller coupledto the cache storage wherein the cache controller is operable to receivea memory operation that specifies a key, a memory address, and a firstset of data, retrieve a second set of data corresponding to the memoryaddress, compare the second set of data to the key, based on the secondset of data corresponding to the key, cause the first set of data to bestored at the memory address, and based on the second set of data notcorresponding to the key, complete the memory operation without causingthe first set of data to be stored at the memory address.

Example 2 includes the system of example 1, further including a storagequeue for the cache storage, the storage queue including a latch tointerface with a tag random access memory (RAM) to retrieve the secondset of data from the cache storage, an atomic compare component, thecache controller to cause the atomic compare component to compare thesecond set of data to the key, and if the key does not match the secondset of data, discard the first set of data, and an arbitration managerto, if the key matches the second set of data, store the first set ofdata at the memory address in the cache storage.

Example 3 includes the system of example 1, wherein the cache storage isat least one of a main cache storage or a victim cache storage.

Example 4 includes the system of example 2, wherein the latch is a firstlatch, the atomic compare component to obtain (a) the second set of datafrom the cache storage via an error detection and correction circuit and(b) the atomic compare and swap command from the first latch via asecond latch.

Example 5 includes the system of example 1, wherein the cache controlleris operable to complete the memory operation based on a singleinstruction from a central processing unit at a single cycle.

Example 6 includes the system of example 1, further including amodified, exclusive, shared, invalid (MESI) component to determine astate of the memory address of the memory operation, and the cachecontroller operable to, if the memory address of the memory operationcorresponds to a shared state, provide miss instructions to anothercache, the miss instructions including an exclusive state request.

Example 7 includes the system of example 6, wherein the cache controlleris to cause an arbitration manger to, if the first data matches the key,store the first set of data at the memory address in the cache storageafter the exclusive state request has been granted from the other cache.

Example 8 includes the system of example 6, wherein the cache controllercauses a tag RAM to retrieve the second set of data from the cachestorage from the memory address after the exclusive state request hasbeen granted from the other cache.

Example 9 includes a storage queue for a cache storage, the storagequeue comprising a latch to retrieve a memory operation that specifies akey, a memory address, and a first set of data, and retrieve a secondset of data corresponding to the memory address, and an atomic comparecomponent to compare the second set of data to the key, based on thesecond set of data corresponding to the key, cause the first set of datato be stored at the memory address, and based on the second set of datanot corresponding to the key, complete the memory operation withoutcausing the first set of data to be stored at the memory address.

Example 10 includes the storage queue of example 9, wherein the cachestorage is at least one of a main cache storage or a victim cachestorage.

Example 11 includes the storage queue of example 9, wherein the latch isa first latch, the atomic compare component to obtain (a) the second setof data from the cache storage via an error detection and correctioncircuit and (b) the atomic compare and swap command from the first latchvia a second latch.

Example 12 includes the storage queue of example 9, wherein, if thefirst data matches the key, the storage queue performs the atomiccompare and swap command based on a single instruction from a centralprocessing unit at a single cycle.

Example 13 includes the storage queue of example 9, further including amodified, exclusive, shared, invalid (MESI) component to determine astate of the memory address of the memory operation, and an interfaceto, if the memory address of the memory operation corresponds to ashared state, provide miss instructions to another cache, the missinstructions including an exclusive state request.

Example 14 includes the storage queue of example 13, further includingan arbitration manager to, if the first data matches the key, store thefirst set of data at the memory address after the exclusive staterequest has been granted from the other cache.

Example 15 includes the storage queue of example 13, wherein the latchis to interface with a tag RAM to read the second set of data after theexclusive state request has been granted from the other cache.

Example 16 includes a method comprising receiving a memory operationthat specifies a key, a memory address, and a first set of data,retrieving a second set of data corresponding to the memory address,comparing the second set of data to the key, based on the second set ofdata corresponding to the key, causing the first set of data to bestored at the memory address, and based on the second set of data notcorresponding to the key, completing the memory operation withoutcausing the first set of data to be stored at the memory address.

Example 17 includes the method of example 16, further includinginterfacing with a tag random access memory (RAM) to retrieve the secondset of data from a cache storage, comparing the second set of data tothe key, and if the key does not match the second set of data,discarding the first set of data, and if the key matches the second setof data, storing the first set of data at the memory address in thecache storage.

Example 18 includes the method of example 17, further including (a) thesecond set of data via an error detection and correction circuit and (b)the memory operation from a central processing unit.

Example 19 includes the method of example 16, wherein the completing ofthe memory operation is based on a single instruction from a centralprocessing unit at a single cycle.

Example 20 includes the method of example 16, further includingdetermining a state of the memory address of the memory operation, andif the memory address of the memory operation corresponds to a sharedstate, providing miss instructions to another cache, the missinstructions including an exclusive state request.

Methods and Apparatus for Inflight Data Forwarding and Invalidation ofPending Writes in Store Queue

In examples disclosed herein, when the CPU 102 issues a read operation,the tag RAM accesses 204, 206 determine if the read operation hits ormisses the main storage element 214 and/or the victim storage element218. In examples where the tag RAM accesses 204, 206 determine that theread common misses both the main storage element 214 and the victimstorage element 214, the cache controller 220 sends an operation to themain storage element 214 to create a victim (e.g., to determine a linein the main storage element 214 to evict). In some examples, problemsmay arise when the main storage element 214 evicts a line thatcorresponds to outstanding writes. For example, a line in the mainstorage element 214 that is currently having data written to it by thestore queue 212 can have outstanding writes located in any of thelatches 402 a-d. In some examples, an error may occur when a new addressreplaces the line in the main storage element 214 that was evicted andthe store queue 212 is still attempting to write data from a previouswrite operation into the same line.

Examples disclosed herein include a read-invalidate operation to beissued to the store queue 212 when the cache controller 220 determinesthat a read operation is a read miss. The cache controller 220 sends theread-invalidate operation to the store queue 212 when the main storageelement 214 creates a victim. The read-invalidate operation notifies thestore queue 212 to compare the address of the victim to all theaddresses stored in the latches 402 a-d. If any of the addresses in thelatches 402 a-d match the address of the victim, the prioritymultiplexer 418 sends the data in the matching address to the latch 402e to transmit the data to MUX circuit 314. Such an operation may bereferred to as data forwarding of in-flight data. For example, when thepriority multiplexer 418 sends data corresponding to the victim to theMUX circuit 314 via the latch 402 e, the MUX circuit 314 forwards thedata of the victim to the victim storage element 218 and/or the L2 cache112. Additionally, the read-invalidate operation invalidates the datastored in the latches 402 a-d when the latches 402 a-d include theaddress corresponding to the victim. For example, each of the latches402 a-d include a valid tag. The valid tag indicates to the latches 402a-d whether data is to be stored in the main storage element 214. Whenthe read-invalidate operation invalidates the valid tag, the latches 402a-d discontinue writing the invalid data to main storage element 214.

In an example operation, the CPU 102 issues a write operation. In someexamples, the write operation corresponds to an Address A. For example:

Write operation=Write(Address A):Data 1//write Data 1 to cache linecorresponding to Address A

The store queue 212 obtains the write operation and begins the processof writing data to Address A of the main store element 214. In someexamples, the Address A corresponds to cache line 1 in the main storageelement 214. Subsequently, the CPU 102 issues a read operation. In someexamples, the read operation corresponds to an Address B. For example:

Read operation=Read(Address B)//read Data 2 in cache line correspondingto Address B

The example tag RAM accesses 204, 206 check the addresses in the tag RAM208 and the tag RAM 210 and determine neither of the tag RAMs 208, 210include Address B. The cache controller 220 obtains the read-miss resultfrom the tag RAM accesses 204, 206 and issues an allocate operation todetermine a victim in the main storage element 214 to evict to thevictim storage element 218 and/or the L2 cache 112. When the cachecontroller 220 obtains a response corresponding to a victim, the cachecontroller 220 issues a read-invalidate operation to the store queue212.

The read port 424 of the store queue 212 obtains the read-invalidateoperation and obtains the address of the victim. The read port 424 sendsthe address of the victim to the data store 416 to be compared to all ofthe addresses stored in the latches 402 a-d. If the data store 416determines any of the addresses stored in the latches 402 a-d match theaddress of the victim, the data store 416 outputs an operation to thepriority multiplexer 418 to send the data corresponding to the victimaddress to the latch 402 e. The latch 402 e forwards the data to the MUXcircuit 314 to send to the victim storage element 218 and/or the L2cache 112.

Additionally, in response to the addresses stored in the latches 402 a-dmatching the victim address, the latches 402 a-d invalidate the datacorresponding to the victim address. For example, the valid tag in thelatches 402 a-d are updated to indicate that the data in the latchcorresponding to the victim address is invalid. In this example, thestore queue 212 will not attempt to write that data to the cache linecorresponding to the previous address that was evicted.

Example methods, apparatus, systems, and articles of manufacture forinflight data forwarding and invalidation are disclosed herein. Furtherexamples and combinations thereof include the following:

Example 1 includes an apparatus comprising a cache storage, a cachecontroller coupled to the cache storage and operable to receive a firstmemory operation, determine that the first memory operation correspondsto a read miss in the cache storage, determine a victim address in thecache storage to evict in response to the read miss, issue aread-invalidate command that specifies the victim address, compare thevictim address to a set of addresses associated with a set of memoryoperations being processed by the cache controller, and in response tothe victim address matching a first address of the set of addressescorresponding to a second memory operation of the set of memoryoperations, provide data associated with the second memory operation.

Example 2 includes the apparatus of example 1, wherein the cachecontroller is to issue the read-invalidate command when a tag randomaccess memory access issues a read-miss.

Example 3 includes the apparatus of example 1, wherein the cachecontroller is to determine the victim address to evict from the cachestorage to make room for a data of a third memory operation.

Example 4 includes the apparatus of example 1, wherein the cachecontroller is operable to discontinue writing data associated with thesecond memory operation in the cache storage.

Example 5 includes the apparatus of example 1, further including a firstlatch, a second latch, a third latch, and a fourth latch, wherein thefirst latch, the second latch, the third latch, or the fourth latch isto store data for the victim address.

Example 6 includes the apparatus of example 5, wherein the first latch,the second latch, the third latch, and the fourth latch include a validtag that is to be updated to invalid when any of the first latch, thesecond latch, the third latch, or the fourth latch store the data forthe victim address.

Example 7 includes the apparatus of example 1, further including a readport to initiate the comparison between the victim address and the setof addresses associated with the set of memory operations beingprocessed by the cache controller when the read port obtains theread-invalidate command and the victim address.

Example 8 includes a method to invalidate a write operation, the methodcomprising receiving a first memory operation, determining that thefirst memory operation corresponds to a read miss in a cache storage,determining a victim address in the cache storage to evict in responseto the read miss, issuing a read-invalidate command that specifies thevictim address, comparing the victim address to a set of addressesassociated with a set of memory operations being processed by a cachecontroller, and in response to the victim address matching a firstaddress of the set of addresses corresponding to a second memoryoperation of the set of memory operations, providing data associatedwith the second memory operation.

Example 9 includes the method of example 8, further including issuingthe read-invalidate command when a tag random access memory accessissues a read-miss.

Example 10 includes the method of example 8, further includingdetermining the victim address to evict from the cache storage to makeroom for a data of a third memory operation.

Example 11 includes the method of example 8, further includingdiscontinuing writing the data associates with the second memoryoperation in the cache storage.

Example 12 includes the method of example 8, further including storingdata for the victim address in at least one of a first latch, a secondlatch, a third latch, and a fourth latch.

Example 13 includes the method of example 12, further including updatinga valid tag of the first latch, the second latch, the third latch, orthe first latch to invalid when any of the first latch, the secondlatch, the third latch, and the fourth latch store the data for thevictim address.

Example 14 includes the method of example 8, further includinginitiating the comparison between the victim address and the set ofaddresses associated with the set of memory operations being processedby the cache controller when a read port obtains the read-invalidatecommand and the victim address.

Example 15 includes a system comprising a central processing unit tooutput a first memory operation, a cache coupled to the centralprocessing unit, the cache including a cache storage, a cache controllercoupled to the cache storage and operable to receive the first memoryoperation, determine that the first memory operation corresponds to aread miss in the cache storage, determine a victim address in the cachestorage to evict in response to the read miss, issue a read-invalidatecommand that specifies the victim address, compare the victim address toa set of addresses associated with a set of memory operations beingprocessed by the cache controller, and in response to the victim addressmatching a first address of the set of addresses corresponding to asecond memory operation of the set of memory operations, provide dataassociated with the second memory operation and invalidate the secondmemory operation.

Example 16 includes the system of example 15, wherein the cache is afirst cache and wherein the first cache is operable to retrieve dataassociated with the first memory operation from a second cache inresponse to the cache storage not including the data associated with thefirst memory operation.

Example 17 includes the system of example 15, wherein the cache includesa store queue to store write data of the second memory operation intothe cache storage in multiple clock cycles, each clock cycle writing atleast one portion of the data associated with the second memoryoperation to the cache storage.

Example 18 includes the system of example 17, wherein the cache is afirst cache and wherein the cache controller is operable to provideportions of data remaining in the store queue to a second cache forstoring when the second memory operation is invalidated.

Example 19 includes the system of example 15, wherein the cache includesa store queue to store outstanding writes, the second memory operationcorresponding to an outstanding write.

Example 20 includes the system of example 15, wherein the centralprocessing unit outputs the first memory operation subsequently tooutputting the second memory operation. FIG. 5 illustrates an examplevictim cache-based section of the level one (L1) cache 110 of FIGS. 1and 3. FIG. 5 includes the tag RAM 210, the victim storage 218, the MESIRAM 300, the example hit/miss comparison logic 306 a, 306 b, 306 c, theexample replacement policy 308 (e.g., the replacement policy component308), the example address encoders 326 a, 326 b, 326 c, examplemultiplexers (MUXs) 330 a, 330 b, 330 c, the example address reads 332a, 332 b, 332 c, an example scalar interface 502, an example vectorinterface 504, an example snoop address component 506, and an exampleresponse multiplexer 508. FIG. 5 illustrates a victim cache system thatsupports dual data paths and a coherency pipeline.

In FIG. 5, the example scalar interface 502 is an interface coupling theL1 cache 110 of the data cache 108 of FIG. 1 to the example processingcore 104 a. In some examples, the scalar interface 502 is an interfacecorresponding to a first data path (DP0) in the dual data path victimcache system. In some examples, the scalar interface 502 is an interfacecorresponding to a second data path (DP1) in the dual data path cachesystem. The example scalar interface 502 is a 64-bit wide bidirectionaland/or unidirectional interface. Alternatively, the example scalarinterface 502 may support a different quantity of bits (e.g., 32 bits,128 bits, etc.). In some examples, the scalar interface 502 receivesand/or obtains data from the core 104 a. In some examples, the scalarinterface 502 sends data from the victim storage 218 to the core 104 a.The example scalar interface 502 is coupled to the example tag RAM 210,and comparison logic 306 to compare an address from the CPU 102 toaddresses in the tag RAM 210.

In FIG. 5, the example vector interface 504 is an interface coupling theL1 cache 110 of the data cache 108 of FIG. 1 to the example processingcore 104 a. In some examples, the vector interface 504 is an interfacecorresponding to a second data path (DP1) in the dual data path cachesystem. In some examples, the vector interface 504 is an interfacecorresponding to a first data path (DP0) in the dual data path cachesystem. The example vector interface 504 is a 512-bit wide interface.Alternatively, the example vector interface 504 may support a differentquantity of bits (e.g., 256 bits, 1024 bits, etc.). In some examples,the vector interface 504 receives and/or obtains data from the core 104a. In some examples, the vector interface 504 sends data from the victimstorage 218 to the core 104 a. The example vector interface 504 iscoupled to the example tag RAM 210, the snoop address component 506, andcomparison logic 306 b to compare an address from the CPU 102 toaddresses from the tag RAM 210. In some examples, the scalar interface502 and the vector interface 504 are implemented by the CPU interface202 (FIG. 2). For example, the scalar interface 502 and the vectorinterface 504 can be included in the CPU interface 202.

In FIG. 5, the example tag RAM 210 is connected to the exampleinterfaces 502, 504. However, in some examples, the tag RAM 210 may becoupled to the interfaces 502, 504 via the example victim tag RAM access206 (FIG. 2). The example tag RAM 210 is a dual-port fully associatedtag RAM to support the dual data paths (e.g., scalar data path andvector data path). As used herein, a fully associated tag RAM 210permits data from the main storage 214 (FIG. 2) to be stored in anycache block rather than forcing each memory address into one particularblock. In some examples, because the tag RAM 210 is fully associated,the victim storage 218 is also fully associated.

In FIG. 5, the comparison logic 306 a is connected to the scalarinterface 502, the tag RAM 210, the address encoder 326 a, and thereplacement policy component 308. The comparison logic 306 b isconnected to the vector interface 504, the tag RAM 210, the addressencoder 326 b, and the replacement policy component 308. The comparisonlogic 306 a, 306 b supports both scalar and vector data paths. Forexample, the comparison logic 306 can compare scalar data to data of tagRAM 210 and/or vector data to the data of the tag RAM 210. Thecomparison logic 306 provides a hit or miss output to the replacementpolicy component 308 and the address encoders 326 a, 326 b. In someexamples, the comparison logic 306 provides the hit or miss output tothe multiplexers 330 a, 330 b.

In FIG. 5, the example replacement policy component 308 is coupled tothe comparison logic 306 a, 306 b. The example replacement policycomponent 308 is control/decision making logic. The example replacementpolicy component 308 dictates the entries (e.g., the data) of theexample victim storage 218 based on a plurality of inputs. For example,the replacement policy component 308 can determine whether the cachecontroller 220 (FIG. 2) is to remove and/or enter entries to/from thevictim storage 218. The control logic of the replacement policycomponent 308 is configured to resolve address conflicts between the 2addresses (e.g., scalar and vector) in such a way that data-consistencyis maintained. FIG. 6 illustrates the control logic of the examplereplacement policy component 308.

In FIG. 5, the example address encoders 326 a, 326 b encode memoryaddresses into a form interpretable by the victim storage 218. Forexample, the address encoders 326 a, 326 b can operate similarly to theaddress encoder 326 of FIGS. 3A-3D. The example address encoders 326 a,326 b output encoded addresses to the multiplexers 330 a, 330 b. Forexample, address encoder 326 a can output encoded memory addresses tomultiplexer 330 a and address encoder 326 b can output encoded memoryaddresses to multiplexer 330 b.

In FIG. 5, the multiplexers 330 a, 330 b select an address in responseto executing the comparison logic 306 a, 306 b. For example, themultiplexer 330 a can obtain an input from the comparison logic 306 acorresponding to a hit and therefore select the encoded address from theaddress encoder 326 a. Additionally and/or alternatively, themultiplexer 330 a may obtain an input from the comparison logic 306 acorresponding to a miss and therefore select the memory address chosenby the replacement policy component 308. The example multiplexers 330 a,330 b are coupled to address reads 332 a, 332 b.

In FIG. 5, the example address reads 332 a, 332 b read the addressvalues selected by the multiplexers into the victim storage 218. Forexample, the address reads 332 a, 332 b can identify addresses that areto be stored and/or removed from the victim storage 218.

In FIG. 5, the example victim storage 218 is a fully associative cache.For example, the fully associated victim storage 218 can place data,when data is fetched (e.g., victimized) from the main storage 214, inany unused block of the cache. The placement of the data in the victimstorage 218 is based on the replacement policy component 308. Forexample, the replacement policy component 308 can determine when andwhere a line of data from the main storage 214 should be placed in thevictim storage 218. In some examples, when the address reads 332 a, 332b read data into the victim storage 218, the victim storage 218 outputsa response. In some examples, the victim storage 218 generates a DP0response, a DP1 response, and a snoop response to be transmitted to theL2 data cache 112. In some examples, the responses include datarequested by the CPU 102. For example, based on the address reads 332 a,332 b, the victim storage 218 can output data from a memory addresslocation if the CPU 102 has requested such data. Additionally and/oralternatively, based on the address reads 332 a, 332 b, the victimstorage 218 can output eviction data to the L2 cache 112 if thereplacement policy component 308 is replacing data in the victim storage218.

In FIG. 5, the example snoop address component 506 is implemented by asnoop data path and/or otherwise interface. In addition to the two CPUdata paths (e.g., DP0 and DP1), the L1 cache 110 includes the snoop datapath to add coherency to the L1 cache 110. The example snoop addresscomponent 506 is connected to the tag RAM 210 and comparison logic 306c. In some examples, the snoop address component 506 obtains an examplesnoop request address issued by a higher-level data cache (e.g., the L2data cache 112) that issues an address read to the tag RAM 210. Forexample, the snoop address component 506 attempts to read a memoryaddress from the tag RAM 210. Additionally, the snoop address component506 provides the address read to the comparison logic 306 c. The snoopaddress component 506 and more generally, the coherency pipeline, isutilized to store the MESI state of every cache line in the victimstorage 218 in the MESI RAM 300. By storing the MESI state of everycache line in the MESI RAM 300, the victim cache system supportscoherency.

In FIG. 5, the example MESI RAM 300 is connected to the comparison logic306 c. The example MESI RAM 300 tracks the states of a cache line in themain storage 214 and the victim storage 218 by marking the cache line asmodified, exclusive, shared, or invalid based on the comparison logic306 c. For example, when the snoop address component 506 issues a readto the tag RAM 210, the tag RAM 210 returns or does not return thecorrect memory address. Thus, the comparison logic 306 c compares thememory address of the snoop issued read and the tag RAM 210 results todetermine the state of the cache line.

In the example topology illustrated in FIG. 5, the response multiplexer508 is coupled to the victim storage 218 and to the victim cache storequeue 216. In this manner, the response multiplexer 508 is configured toselect between the data obtained by the victim storage 214 and/or thedata obtained by the victim cache store queue 216 to transmit the datamost recent to the system. Example operational description of thepriority multiplexer 508 is described below.

Methods and Apparatus for Multi-Banked Victim Cache with Dual Datapath

In some victim caches, there is not support for a multi-bankarchitecture. For instance, a victim cache may be a monolithic storagedevice that does not support multiple accesses by a processor (e.g., aCPU) during the same clock cycle. For example, a request to access datain a single victim cache can lock up the entire victim cache. In suchexamples, there is a single register file capable of supporting one fullvictim cache line access per clock cycle. In some such examples, anentire victim cache line associated with the single victim storage canbe locked to service the request because the single register file isallocated to the victim storage data bank that received such a request.

Examples disclosed herein include a multi-banked victim cache with adual datapath. In some disclosed examples, the victim storage 218 ofFIG. 2 has a plurality of banks and, thus, is multi-banked, or has amulti-bank data or memory structure. Advantageously, the multi-bankstructure of the victim storage 218 can effectuate support for two ormore accesses (e.g., CPU accesses) per clock cycle. Advantageously, themulti-bank structure of the victim storage 218 allows the two or moreaccesses to be serviced and/or fulfilled without performance overhead.

In some disclosed examples, the victim storage 218 has a two-port fullyassociative tag ram (e.g., the tag ram 210 of FIG. 2). In some disclosedexamples, hit/miss comparison is supported for both scalar and vectoraddresses. In such disclosed examples, based on the hit/miss decision oneach of the datapaths (e.g., the scalar data path, the vector data path,etc.) the victim storage 218 is locked. In an example where an access tothe victim storage 218 is a hit, then the location of the hit entry isselected. In an example, where an access to the victim storage 218 is amiss, then allocation policy is checked for a particular set of thevictim storage 218.

In some disclosed examples, in a subsequent pipe stage, the selectedsets of the victim storage 218 for both addresses are read andresponse(s) is/are given back to the CPU. In some disclosed examples,the set selection logic resolves address conflict between the twoaddresses (e.g., the scalar address and the vector address) in such amanner that data-consistency is maintained. In some disclosed examples,the control logic resolves address conflict as well.

In some disclosed examples, bank arbitration logic calculates and/orotherwise determines the banks required for each of the addresses andselects the read on each of the banks. In some disclosed examples, thecontrol logic resolves any bank conflict between the two addresses toeffectuate serialization of the two memory operations. In some disclosedexamples where both datapaths access the same address, the control logiccan effectuate not issuing multiple allocation requests for the sameaddress. Once the data is read from the victim storage 218, example datamuxing logic can fold the data into the correct data lanes beforereturning the data back to the CPU as read response(s).

FIG. 7A is a schematic illustration of a first example encapsulated datacache system 700. The first encapsulated data cache system 700 can be anexample circuit implementation of the L1 cache 110 of FIG. 1 orportion(s) thereof, and/or, more generally, the data cache 108 of FIG. 1or portion(s) thereof. The first encapsulated data cache system 700 isencapsulated to provide a unified storage view to an external system(e.g., one or more CPUs, one or more processors, external hardware,etc.). For example, the first encapsulated data cache system 700 can beencapsulated using firmware, software, hardware logic, etc., and/or acombination thereof to encapsulate and/or otherwise abstract allcomplexity related to read after write (RAW) hazards, write after write(WAW) hazards, data forwarding, etc. Advantageously, the unifiedarchitecture depicted in the example of FIG. 7A can provide separateports to an external system (e.g., the CPU 102) to simplify obtainingaccess to the most recent versions of data of interest.

In the example of FIG. 7A, the first encapsulated data cache system 700includes the victim cache store queue 216 of FIG. 2 and the victimstorage 218 of FIG. 2. In FIG. 7A, the victim cache store queue 216includes a plurality of first example independently addressable banks(e.g., data banks, store banks, data store banks, etc.) 702. Forexample, the first independently addressable banks 702 can be bankqueues, bank sub-queues, etc. In such examples, the bank queues, thebank sub-queues, etc., can include a plurality of storage elements, asdepicted below in FIG. 7C and/or FIG. 7E. The first independentlyaddressable banks 702 are victim cache store queue banks (e.g., victimcache store queue data banks, victim cache bank queues, victim cachebank sub-queues, etc.). In FIG. 7A, the victim cache store queue 216includes 16 of the victim cache store queue banks 702. Alternatively,there may be fewer or more than 16 instances of the victim cache storequeue banks 702.

In FIG. 7A, the victim storage 218 includes a plurality of secondexample independently addressable banks (e.g., data banks, store banks,data store banks, etc.) 704. The second independently addressable banks704 are victim storage banks (e.g., victim storage data banks). In FIG.7A, the victim storage 218 includes 16 of the victim storage banks 704.Alternatively, there may be fewer or more than 16 instances of thevictim storage banks 704. For example, the victim cache store queue 216can include a plurality of bank queues or bank sub-queues including afirst bank queue or a first bank sub-queue (e.g., VICTIM CACHE STOREQUEUE: BANK 1) and the victim storage 218 can include a plurality ofdata banks including a first data bank (e.g., VICTIM STORAGE: BANK 1).

In some examples, the victim cache store queue 216 and the victimstorage 218 each have 256 rows with each row having a line width of 1024bits, but being divided into 16 banks as illustrated in FIG. 7A, with 64bits per row in a given bank. In some examples, the victim cache storequeue 216 and the victim storage 218 each have 384 rows with each rowhaving a line width of 1024 bits, but being divided into 16 banks asillustrated in FIG. 7A, with 64 bits per row in a given bank. Of course,the cache size described in the above examples are only two examples andthe disclosure is not limited to any particular cache line width, numberof banks, or rows, etc. As depicted in FIG. 7A, each of the first banks702 correspond to one of the second banks 704. For example, a first bank(BANK 1) of the victim cache store queue 216 is in circuit with a firstbank (BANK 1) of the victim storage 218 and, thus, corresponds with thefirst bank of the victim storage 218.

Advantageously, the multi-bank structure of the victim cache store queue216, the victim storage 218, and/or, more generally, the firstencapsulated data cache system 700, can service read and writeoperations that are sent to the banks in parallel. In some examples,each bank arbitrates its own processes in response to the read and/orwrite operations. By allowing each bank of the first encapsulated datacache system 700 to operate independently, operation of the firstencapsulated data cache system 700 is more efficient since an entirecache line is not locked up when a request is received. Rather, only theportion of the cache line allocated to the bank that received such arequest would be locked.

FIG. 7C depicts an example victim cache multi-bank structure 720. Insome examples, the L1 cache 110, the L2 cache 112, and/or the L3 cache114 of FIG. 1 can have the victim cache bank structure 720. In someexamples, the victim cache store queue 216 of FIG. 2 and/or the victimstorage 218 of FIG. 2 can have the victim cache multi-bank structure720. For example, the victim cache multi-bank structure 720 can be anexample implementation of the victim cache store queue 216 and/or thevictim storage 218.

The victim cache multi-bank structure 720 is a data or memory structurethat includes 16 example banks (Banks 0-15) 722, with each of the banks722 having a data width of 64 bytes (e.g., bytes 0-7). Each of the banks722 includes 16 example rows (Rows 0-15) 724, with each of the rows 724having a data width of 128 bytes (e.g., 128 bytes=8 bytes/bank*16banks). In FIG. 7C, each of the banks 722 can store 128 bytes (e.g., 128bytes=8 bytes/row*16 rows). In FIG. 7C, the victim cache multi-bankstructure 720 can store 2048 bytes (e.g., 2048 bytes=128 bytes/bank*16banks). The victim cache multi-bank structure 720 is independentlyaddressable by bank. For example, the first row of the rows 724 has astarting row address of 0 and an ending row address of 127, a second rowof the rows 724 has a starting row address of 128 and an ending rowaddress of 255, etc.

In some examples, a cache line can be 128 bytes of data that fits in awidth of memory (e.g., DRAM) or storage unit (e.g., the main storage214, the victim storage 218, etc.). In the example of FIG. 7C, a cacheline can consume an entire row of the victim cache bank structure 720.For example, a cache line can use one of the rows 724 of 16 banks, whereeach bank is 8 bytes wide. Advantageously, the victim cache bankstructure 720 can enable 16 different cache lines to access data storedtherein.

FIG. 8A illustrates a schematic illustration of example victim cache tag(VCT) random access memory (RAM) 800. The VCT RAM 800 can be an exampleimplementation of the tag ram 210 of FIG. 2. For example, the VCT RAM800 can store addresses of data stored in the victim cache store queue216, the victim storage 218, etc., of FIG. 2. The VCT RAM 800 is amulti-bank VCT RAM. For example, the VCT RAM 800 can include a pluralityof banks (e.g., data banks, memory banks, etc.), such as 16 banks,although the VCT RAM 800 can have a different quantity of banks.

The VCT RAM 800 includes example allocation ports 802, 804, 806including a first example allocation port (AP0) 802, a second exampleallocation port (AP1) 804, and a third example allocation port (AP2)806. The VCT RAM 800 includes example read ports 808, 810, 812 includinga first example read port (RP0) 808, a second example read port (RP1)810, and a third example read port (RP2) 812. The VCT RAM 800 includesan example LRU read port 814. The VCT RAM 800 includes example outputports 816, 818, 820, 822 including a first example output port (OP0)816, a second example output port (OP1) 818, a third example output port(OP2) 820, and a fourth example output port (OP3) 822. Alternatively,VCT RAM 800 may fewer or more allocation ports, read ports, LRU readports, and/or output ports than depicted in FIG. 8A.

The VCT RAM 800 includes the allocation ports 802, 804, 806 to fill thevictim storage 218. For example, the allocation ports 802, 804, 806 canbe configured to receive requests from external hardware (e.g., the CPU102, the main storage 214, etc.) to store data in the victim storage218. The first allocation port 802 is configured to receive firstexample data 824. For example, the first allocation port 802 can receivethe first data 824 from the write state machine associated with thescalar data path (DP0). The first data 824 includes WRM_TAG_UPDATE0data, which can be representative of a control signal generated from theCPU interface 202 of FIG. 2 (e.g., the scalar data path (DP0)). Thecontrol signal can be generated to inform the VCT RAM 800 that the CPUinterface 202 has a cache line to be moved from the CPU interface 202 tothe victim storage 218 and, thus, the CPU interface 202 has an addressto be moved from the CPU interface 202 to the tag ram 210. The firstdata 824 includes VTAG_WR_TAG0 data, which can be representative of anaddress (e.g., a tag address) of the VCT RAM 800 that can correspond toan address of data to be stored in the victim cache 218. The first data824 includes VTAG_WR_SET0 data, which can be representative of theaddress of the victim cache 218 of where to store the data (e.g., thevictim cache tag for DP0).

The second allocation port 804 is configured to receive second exampledata 826. For example, the second allocation port 804 can receive thesecond data 826 from the write state machine associated with the vectordata path (DP1). The second data 826 includes WRM_TAG_UPDATE1 data,which can be representative of a control signal generated from the CPUinterface 202 of FIG. 2 (e.g., the vector data path (DP1)). The controlsignal can be generated to inform the VCT RAM 800 that the CPU interface202 has a cache line to be moved from the CPU interface 202 to thevictim storage 218 and, thus, the CPU interface 202 has an address to bemoved from the CPU interface 202 to the tag ram 210. The second data 826includes VTAG_WR_TAG1 data, which can be representative of an address(e.g., a tag address) of the VCT RAM 800 that can correspond to anaddress of data to be stored in the victim cache 218. The second data826 includes VTAG_WR_SET1 data, which can be representative of theaddress of the victim cache 218 of where to store the data (e.g., thevictim cache tag for DP1).

The third allocation port 806 is configured to receive third exampledata 828. The third data 828 includes ARB_EVT_TAG_UPDATE data, which canbe representative of a control signal generated from the main storage214. The control signal is an arbitration (ARB) evict (EVT) tag updatecontrol signal, which can be generated to inform the VCT RAM 800 thatthe main storage 214 has a cache line to be moved from the main storage214 to the victim storage 218 and, thus, the main storage 214 has anaddress to be moved from the tag ram 208 to the tag ram 210. The thirddata 828 includes ADP_EVT_WR_TAG data, which can be representative of anaddress (e.g., a tag address) of the VCT RAM 800 that can correspond toan address of data to be stored in the victim cache 218. The third data828 includes ADP_EVT_WR_SET data, which can be representative of theaddress of the victim cache 218 of where to store the data (e.g., thevictim cache tag for the line moved from the main cache to the victimcache). For example, ADP_EVT_WR_TAG and ADP_EVT_WR_SET data can bereferred to as address datapath (ADP) data. The first data 824, thesecond data 826, and/or the third data 828 can be one or more datapackets, one or more signals based on a communication protocol (e.g., aninter-integrated circuit (I2C) protocol), etc.

The VCT RAM 800 includes the read ports 808, 810, 812 to provideinterfaces for which external hardware (e.g., the CPU 102) can requestto read and/or otherwise access data stored in the victim storage 218.The first read port 808 is configured to receive fourth example data830. For example, the first read port 808 can receive the fourth data830 from the scalar interface 502 of the CPU 102. The fourth data 830includes ADP_ADDR_E2_DP0 data, which can be representative of an addressof the victim storage 218 that the scalar interface 502 requests accessto.

The second read port 810 is configured to receive fifth example data832. For example, the second read port 810 can receive the fifth data832 from the vector interface 504 of the CPU 102. The fifth data 832includes ADP_ADDR_E2_DP1 data, which can be representative of an addressof the victim storage 218 that the vector interface 504 requests accessto.

The third read port 812 is configured to receive sixth example data 834.For example, the third read port 812 can receive the sixth data 834 fromthe snoop address component 506 of FIG. 5 (e.g., the snoop interface).The sixth data 834 includes SNP_ADDR_E2_DP0 data, which can berepresentative of an address of the victim storage 218 that the snoopaddress component 506 requests access to.

The LRU read port 814 is configured to receive seventh example data 836.For example, the LRU read port 814 can receive the seventh data 836 fromthe replacement policy component 308 of FIGS. 3A-3D. The seventh data836 includes LRU_SET_DP0 and LRU_SET_DP1, which can be representative ofrespective addresses associated with the least randomly used (LRU) cachelines of the victim storage 218. For example, the LRU read port 814 canbe a victim least randomly used (VLRU) read port configured to receiveLRU data from the replacement policy component 308.

The VCT RAM 800 includes the output ports 816, 818, 820, 822 to transmitoutputs to external hardware (e.g., the CPU 102, the main storage 214,etc.) in response to a read request or a write request (e.g., anallocation request) associated with the victim storage 218. The firstoutput port 816 is configured to transmit first example output data 838.For example, the first output port 816 can transmit the first outputdata 838 to the scalar interface 502. The first output data 838 includesVTAG_HIT_DP0 data, which can indicate that data requested by the scalarinterface 502 is stored in the victim storage 218. The first output data838 includes VTAG_MISS_DP0 data, which can indicate that the datarequested by the scalar interface 502 is not stored in the victimstorage 218. The first output data 838 includes VTAG_SET_DP0 data, whichcan be representative of the address in the victim storage 218 where thedata requested by the scalar interface 502 is stored.

The second output port 818 is configured to transmit second exampleoutput data 840. For example, the second output port 818 can transmitthe second output data 840 to the vector interface 504. The secondoutput data 840 includes VTAG_HIT_DP1 data, which can indicate that datarequested by the vector interface 504 is stored in the victim storage218. The second output data 840 includes VTAG_MISS_DP1 data, which canindicate that the data requested by the vector interface 504 is notstored in the victim storage 218. The second output data 840 includesVTAG_SET_DP1 data, which can be representative of the address in thevictim storage 218 where the data requested by the vector interface 504is stored.

The third output port 820 is configured to transmit third example outputdata 842. For example, the third output port 820 can transmit the thirdoutput data 842 to the replacement policy component 308. The thirdoutput data 842 includes VTAG_ADDR_DP0 data, which can be representativeof the address of the victim storage 218 that is associated with therequest LRU_SET_DP0 by the replacement policy component 308 received atthe LRU read port 814.

The fourth output port 822 is configured to transmit fourth exampleoutput data 844. For example, the fourth output port 822 can transmitthe fourth output data 844 to the replacement policy component 308. Thefourth output data 844 includes VTAG_ADDR_DP1 data, which can berepresentative of the address of the victim storage 218 that isassociated with the request LRU_SET_DP1 by the replacement policycomponent 308 received at the LRU read port 814.

FIG. 8B illustrates another schematic illustration of the exampleimplementation of the VCT RAM 800 of FIG. 8A. For example, FIG. 8B cancorrespond to the victim cache-based section of the L1 cache 110 of FIG.5, or portion(s) thereof.

FIG. 8B depicts another example implementation of the VCT RAM 800 ofFIG. 8A. In FIG. 8B, the VCT RAM 800 includes 16 example sets 846. Forexample, the sets 846 include a first set VCT_ADDR[0], a second setVCT_ADDR[1], etc. Alternatively, the VCT RAM 800 may include fewer ormore than 16 of the sets 846.

The VCT RAM 800 is victim cache tag storage configured to storeaddresses (e.g., tag addresses) that correspond to the sets 846. Each ofthe sets 846 is coupled to a respective one of first example comparators850 and a respective one of second example comparators 852. The firstcomparators 850 can be an example implementation of the comparison logic306 a of FIGS. 3 and/or 5. The second comparators 852 can be an exampleimplementation of the comparison logic 306 b of FIGS. 3 and/or 5. Thefirst set VCT_ADDR[0] is coupled to a first one of the first comparators850 and a first one of the second comparators 852, the second setVCT_ADDR[1] is coupled to a second one of the first comparators 850 anda second one of the second comparators 852, etc.

The first comparators 850 and the second comparators 852 are coupled torespective example address encoder logic circuits 854, 856 including afirst example address encoder logic circuit 854 and a second exampleaddress encoder logic circuit 856. The first comparators 850 are coupledto the first address encoder logic circuit 854. The second comparators852 are coupled to the second address encoder logic circuit 856.

The address encoder logic circuit 854, 856 can be exampleimplementations of the address encoders 326 a, 326 b of FIGS. 3 and/or5. For example, the first address encoder logic circuit 854 can be anexample implementation of the address encoder 326 a. In other examples,the second address encoder logic circuit 856 can be an exampleimplementation of the address encoder 326 b.

A first example multiplexer 858A is coupled to the first address encoderlogic circuit 854. The first address encoder logic circuit 854 includesa first example decoder 860A, a first example inverter (e.g., a logicgate, an inverting logic gate, etc.) 862A, a first example AND gate(e.g., a logic gate, an AND logic gate, etc.) 864A, a first example ORgate (e.g., a logic gate, an OR logic gate, etc.) 866A, a first exampleencoder 868A, a third example comparator 870A, and a fourth examplecomparator 872A.

FIG. 8B depicts only one instance each of the first AND gate 864A, thefirst OR gate 866A, the third comparator 870A, and the fourth comparator872A for clarity. However, each of the first AND gate 864A, the first ORgate 866A, the third comparator 870A, and the fourth comparator 872A canbe representative of 16 instances of said component. For example, thefirst AND gate 864A can be representative and/or otherwise implement 16instances of the first AND gate 864A, the first OR gate 866A can berepresentative of and/or otherwise implement 16 instances of the firstOR gate 866A, etc.

The first multiplexer 858A has a first input to receive ADP_ADDR_E2_DP0,which is representative of an address requested by the DP0 interfacefrom the E2 Arbitration stage of FIGS. 3A-3D. The first multiplexer 858Ahas a second input to receive SNP_ADDR_E2_DP0, which is representativeof a snoop address requested by the snoop interface from the E2Arbitration stage of FIGS. 3A-3D. The first multiplexer 858A has aselect input to receive SNP_ADDR_EN_DP0, which is representative of anenable signal from the snoop interface that, when asserted, can invokethe first multiplexer 858A to select the second input. An output of thefirst multiplexer 858A is coupled to inputs of the first comparators850. For example, each of the first comparators 850 can compare anaddress from the output of the first multiplexer 858A to a correspondingone of the sets of the VCT RAM 800. In such examples, a first one of thefirst comparators 850 can compare an address included in ADP_ADDR_E2_DP0to the address stored in VCT_ADDR[0]. In some such examples, the firstone of the first comparators 850 can output and/or otherwise generate alogic one in response to the address from the first multiplexer 858Amatching the address stored in VCT_ADDR[0].

Outputs of the first multiplexer 858A are coupled to a first input ofthe third comparator 870A. An output of an example DP0 read finite-statemachine (FSM) (READ_FSM_DP0) 873 and/or an output of an example DP0write finite-state machine (WRITE_FSM_DP0) 874 is coupled to a secondinput of the third comparator 870A. The DP0 read finite-state machine873 and the DP0 write finite-state machine 874 are hardware implementedfinite-state machines that execute logic on data from the scalarinterface 502 of FIG. 5. For example, the DP0 read finite-state machine873 and/or the DP0 write finite-state machine 874 can transmit one ormore of WRM_TAG_UPDATE0, VTAG_WR_TAG0, and VTAG_WR_SET0 to the thirdcomparator 870A and/or the fourth comparator 872A. The DP0 readfinite-state machine 873 and/or the DP0 write finite-state machine 874can transmit VTAG_WR_TAG0 to a sixth example comparator 872B included inthe second address encoder logic circuit 856. WRM_TAG_UPDATE0,VTAG_WR_TAG0, and VTAG_WR_SET0 are described above in connection withFIG. 8A.

The first decoder 860A is a 4×16 decoder. The first decoder 860A has aninput to receive VTAG_WR_SET0 data, which can be representative of anin-flight address from the scalar interface 502 to the victim storage218. The first decoder 860A has an output coupled to an input of thefirst inverter 862A. The first decoder 860A can convert the in-flightaddress to a bit vector where each bit is inverted by one of the 16instances of the first inverter 862A. An output of the first inverter862A is coupled to a first input of the first AND gate 864A. A secondinput of the first AND gate 864A is coupled to the result bit of the tagcomparison from the first comparators 850 with set 0 (e.g., VCT_ADDR[0])and the output of the first multiplexer 858A. For example, the secondinput of the first AND gate 864A can be configured to receive HIT_DP0data, which can be representative of a 16-bit vector, where each of thebits can correspond to whether the ADP_ADDR_E2_DP0 data is a hit (e.g.,a bit value of 1) or a miss (e.g., a bit value of 0) in the victimstorage 218.

An output of the first AND gate 864A is coupled to a first input of thefirst OR gate 866A. An output of the third comparator 870A is coupled toa second input of the first OR gate 866A. An output of the fourthcomparator 872A is coupled to a third input of the first OR gate 866A.An output of the first OR gate 866A is coupled to an input of the firstencoder 868A. The first encoder 868A is a 16×4 encoder. For example, thefirst encoder 868A can generate HIT_ADDR0 data, which can berepresentative of VTAG_SET_DP0 of FIG. 8A. In such examples, HIT_ADDR0can correspond to the first output data 838 of FIG. 8A.

The second address encoder logic circuit 856 includes a second exampledecoder 860B, a second example inverter (e.g., a logic gate, aninverting logic gate, etc.) 862B, a second example AND gate (e.g., alogic gate, an AND logic gate, etc.) 864B, a second example OR gate(e.g., a logic gate, an OR logic gate, etc.) 866B, a second exampleencoder 868B, a fifth example comparator 870B, and the sixth examplecomparator 872B.

FIG. 8B depicts only one instance each of the second AND gate 864B, thesecond OR gate 866B, the fifth comparator 870B, and the sixth comparator872B for clarity. However, each of the second AND gate 864B, the secondOR gate 866B, the fifth comparator 870B, and the sixth comparator 872Bcan be representative of 16 instances of said component. For example,the second AND gate 864B can be representative and/or otherwiseimplement 16 instances of the second AND gate 864B, the second OR gate866B can be representative of and/or otherwise implement 16 instances ofthe second OR gate 866B, etc.

The second address encoder logic circuit 856 has a first input toreceive ADP_ADDR_E2_DP1, which is representative of an address requestedby the DP1 interface from the E2 Arbitration stage of FIGS. 3A-3D.ADP_ADDR_E2_DP1 is coupled to inputs of the second comparators 852. Forexample, each of the second comparators 852 can compare the addressincluded in ADP_ADDR_E2_DP1 to a corresponding one of the sets of theVCT RAM 800. In such examples, a first one of the second comparators 852can compare an address included in ADP_ADDR_E2_DP1 to the address storedin VCT_ADDR[0]. In some such examples, the first one of the secondcomparators 852 can output and/or otherwise generate a logic one inresponse to the address included in ADP_ADDR_E2_DP1 matching the addressstored in VCT_ADDR[0].

ADP_ADDR_E2_DP1 is coupled to a first input of the fifth comparator870B. An output of an example DP1 read finite-state machine(READ_FSM_DP1) 875 and/or an output of an example DP1 write finite-statemachine (WRITE_FSM_DP1) 876 is coupled to a second input of the fifthcomparator 870B. The DP1 read finite-state machine 875 and the DP1 writefinite-state machine 876 are hardware implemented finite-state machinesthat execute logic on data from the vector interface 504 of FIG. 5. Forexample, the DP1 read finite-state machine 875 and/or the DP1 writefinite-state machine 876 can transmit one or more of WRM_TAG_UPDATE1,VTAG_WR_TAG1, and VTAG_WR_SET1 to the fifth comparator 870B and/or thesixth comparator 872B. The DP1 read finite-state machine 875 and/or theDP1 write finite-state machine 876 can transmit VTAG_WR_TAG1 to thefourth comparator 872A included in the first address encoder logiccircuit 854. WRM_TAG_UPDATE1, VTAG_WR_TAG1, and VTAG_WR_SET1 aredescribed above in connection with FIG. 8A.

The second decoder 860B is a 4×16 decoder. The second decoder 860B hasan input to receive VTAG_WR_SET1 data, which can be representative of anin-flight address from the vector interface 504 to the victim storage218. The second decoder 860B has an output coupled to an input of thesecond inverter 862B. The second decoder 860B can convert the in-flightaddress to a bit vector where each bit is inverted by one of the 16instances of the second inverter 862B. An output of the second inverter862B is coupled to a first input of the second AND gate 864B. A secondinput of the second AND gate 864B is coupled to the result bit of thetag comparison from the second comparators 852 with set 0 (e.g.,VCT_ADDR[0]) and ADP_ADDR_E2_DP1. For example, the second input of thesecond AND gate 864B can be configured to receive HIT_DP1 data, whichcan be representative of a 16-bit vector, where each of the bits cancorrespond to whether the ADP_ADDR_E2_DP1 data is a hit (e.g., a bitvalue of 1) or a miss (e.g., a bit value of 0) in the victim storage218.

An output of the second AND gate 864B is coupled to a first input of thesecond OR gate 866B. An output of the fifth comparator 870B is coupledto a second input of the second OR gate 866B. An output of the sixthcomparator 872B is coupled to a third input of the second OR gate 866B.An output of the second OR gate 866B is coupled to an input of thesecond encoder 868B. The second encoder 868B is a 16×4 encoder. Forexample, the second encoder 868B can generate HIT_ADDR1 data, which canbe representative of VTAG_SET_DP1 of FIG. 8A. In such examples,HIT_ADDR1 can correspond to the second output data 840 of FIG. 8A.

In example operating conditions, the first address encoder logic circuit854 can receive a first read address (e.g., ADP_ADDR_E2_DP0) for a storeinstruction requested by the CPU 102 of FIG. 1, where the first readaddress is received from the E2 pipeline stage (ARBITRATION) of FIGS.3A-3D. In response to the first multiplexer 858A selecting the firstinput, the first multiplexer 858A can transmit the first read address tothe first comparators 850. The first comparators 850 can compare theread address to the respective ones of the sets 846. If, a first one ofthe first comparators 850 determines that the read address matches anaddress stored at the corresponding one of the sets 846, the first oneof the first comparators 850 can assert and/or otherwise output a logicone, otherwise the first one of the first comparators 850 outputs alogic zero. Accordingly, the first comparators 850 can generate HIT_DP0on a 16-bit data bus as a 16-bit vector in response to the comparisons.For example, the 16-bit vector can be an implementation of a train(e.g., a pulse train) of signals representative of a bit vector. Thefirst comparators 850 can transmit HIT_DP0 to the first AND gate 864A.

Portion(s) of the first address encoder logic circuit 854 and/or thesecond address encoder logic circuit 856 are cache hit-miss conversionlogic. For example, the first AND gate 864A, the third comparator 870A,and/or the fourth comparator 872A can be an example implementation ofcache hit-miss conversion logic. In such examples, the second AND gate864B, the fifth comparator 870B, and/or the sixth comparator 872B can bean example implementation of the cache hit-miss conversion logic.

The first AND gate 864A is configured to determine whether to convert ahit (e.g., a cache hit) to a miss (e.g., a cache miss). For example, anew address (VTAG_WR_SET0) can be written to the victim storage 218during the E3 pipeline stage of FIGS. 3A-3D while the first read addressis being processed during the E2 pipeline stage. In such examples, thefirst decoder 860A can convert the new address into a 16-bit value,which can be inverted by the first inverter 862A. The first inverter862A can transmit the inverted 16-bit value to the first input of thefirst AND gate 864A. The first AND gate 864A can assert a logic one inresponse to VTAG_WR_SET0 not matching the address in HIT_DP0 and, thus,does not convert the cache hit to a cache miss. In other examples, thefirst AND gate 864A can output a logic zero in response to VTAG_WR_SET0matching the address in HIT_DP0 and, thus, converts the cache hit to acache miss because the address requested in ADP_ADDR_E2_DP0 has beenoverwritten and is no longer available at that address.

In example operating conditions, the third comparator 870A and the fifthcomparator 870B can be configured to convert a cache miss to a cachehit. For example, the third comparator 870A can determine that the firstread address (ADP_ADDR_E2_DP0) in the VCT RAM 800 requested during theE2 pipeline stage is getting written in the E3 pipeline stage, which isrepresented by VTAG_WR_TAG0. In such examples, the third comparator 870Acan assert a logic one in response to ADP_ADDR_E2_DP0 matchingVTAG_WR_TAG0 and, thus, convert the cache miss to a cache hit andHIT_ADDR0 can be updated with VTAG_WR_SET0 because the data will beavailable when the ADP_ADDR_E2_DP0 address is read during the E3pipeline stage.

In example operating conditions, the fourth comparator 872A and thesixth comparator 872B can be configured to convert a cache miss to acache hit. For example, the fourth comparator 872A can determine thatthe first read address (ADP_ADDR_E2_DP0) in the VCT RAM 800 requestedduring the E2 pipeline stage is getting written in the E3 pipeline stageby the vector interface 504, which is represented by VTAG_WR_TAG1. Insuch examples, the fourth comparator 872A can assert a logic one inresponse to ADP_ADDR_E2_DP0 matching VTAG_WR_TAG1 and, thus, convert thecache miss to a cache hit and HIT_ADDR0 can be updated with VTAG_WR_SET1because the data will be available when the ADP_ADDR_E2_DP0 address isread during the E3 pipeline stage.

In example operating conditions, the first OR gate 866A and the secondOR gate 866B can be configured to generate an output to a correspondingone of the first encoder 868A or the second encoder 868B. For example,the first OR gate 866B can transmit a 16-bit vector representative of acache miss (e.g., 16 bit values of 0) or a cache hit (e.g., 16-bit valueof an address of the cache hit). In such examples, the first encoder868A can encode the 16-bit value from the first OR gate 866A as a 4-bitaddress and, thus, generate HIT_ADDR0. Such example operations can beapplicable to the second OR gate 866B, the second encoder 868B, and/or,more generally, the second address encoder logic circuit 856.

Example methods, apparatus, systems, and articles of manufacture formulti-banked victim cache with dual datapath are disclosed herein.Further examples and combinations thereof include the following:

Example 1 includes a cache system comprising a storage element thatincludes banks operable to store data, ports operable to receive memoryoperations in parallel, wherein each of the memory operations has arespective address, and a plurality of comparators coupled such thateach of the comparators is coupled to a respective port of the ports anda respective bank of the banks and is operable to determine whether arespective address of a respective memory operation received by therespective port corresponds to the data stored in the respective bank.

Example 2 includes the cache system of example 1, further includingvictim cache including victim cache data, and the data is tag datacorresponding to the victim cache data.

Example 3 includes the cache system of example 1, wherein the memoryoperations include a first memory operation, further including cacheincluding cache data, the data is tag data corresponding to the cachedata, and a first comparator of the plurality of the comparators togenerate a signal in response to detecting a cache hit based on firstdata associated with the first memory operation corresponding to thedata in the storage element.

Example 4 includes the cache system of example 1, wherein the pluralityof the comparators is a plurality of first comparators, and furtherincluding an address encoder logic circuit including a decoder having adecoder input and a decoder output, the decoder input coupled to a firstfinite-state machine associated with a scalar interface of a centralprocessing unit, a plurality of inverters having a respective inverterinput and a respective inverter output, the inverter inputs coupled tothe decoder output, a plurality of AND logic gates having a respectivefirst input and a respective second input, a respective one of the firstinputs coupled to a respective one of the inverter outputs, a respectiveone of the second inputs coupled to a respective one of outputs of theplurality of the first comparators, a plurality of second comparatorscoupled to respective ones of the outputs of the plurality of the firstcomparators and the first finite-state machine, and a plurality of thirdcomparators coupled to the respective outputs of the plurality of thefirst comparators and a second finite-state machine associated with avector interface of the central processing unit.

Example 5 includes the cache system of example 4, wherein a first ANDlogic gate of the plurality of the AND logic gates is to output a logiclow signal to convert a cache hit to a cache miss in response to a firstaddress associated with the scalar interface matching a second addressassociated with the cache hit.

Example 6 includes the cache system of example 4, wherein a firstcomparator of the plurality of the second comparators is to output alogic high signal to convert a cache miss to a cache hit in response toa first address associated with the scalar interface matching a secondaddress associated with the cache miss.

Example 7 includes the cache system of example 4, wherein a firstcomparator of the plurality of the third comparators is to output alogic high signal to convert a cache miss to a cache hit in response toa first address associated with the vector interface matching a secondaddress associated with the cache miss.

Example 8 includes the cache system of example 4, wherein the addressencoder logic circuit includes a plurality of OR logic gates having arespective third input, a respective fourth input, and a respectivefifth input, the third inputs coupled to a respective one of outputs ofthe plurality of the AND logic gates, the fourth inputs coupled to arespective one of outputs of the plurality of the second comparators,the fifth inputs coupled to a respective one of outputs of the pluralityof the third comparators, and an encoder having an encoder input and anencoder output, the encoder input coupled to outputs of the plurality ofthe OR logic gates, the encoder output coupled to an input of amultiplexer.

Example 9 includes the cache system of example 1, wherein the pluralityof the comparators is a plurality of first comparators, and furtherincluding an address encoder logic circuit including a decoder having adecoder input and a decoder output, the decoder input coupled to a firstfinite-state machine associated with a vector interface of a centralprocessing unit, a plurality of inverters having a respective inverterinput and a respective inverter output, the inverter inputs coupled tothe decoder output, a plurality of AND logic gates having a respectivefirst input and a respective second input, a respective one of the firstinputs coupled to a respective one of the inverter outputs, a respectiveone of the second inputs coupled to a respective one of outputs of theplurality of the first comparators, a plurality of second comparatorscoupled to respective ones of the outputs of the plurality of the firstcomparators and the first finite-state machine, and a plurality of thirdcomparators coupled to the respective outputs of the plurality of thefirst comparators and a second finite-state machine associated with avector interface of the central processing unit.

Example 10 includes a victim cache system comprising a victim cachestore queue including first data banks, and a victim storage coupled tothe victim cache store queue, the victim storage including second databanks different from the first data banks.

Example 11 includes the victim cache system of example 10, wherein atleast one of the first data banks or the second data banks includes 16data banks.

Example 12 includes the victim cache system of example 10, wherein thefirst data banks includes a first data bank having 8 addresses eachhaving a data width of 1 byte, the first data bank configured to store64 bits.

Example 13 includes the victim cache system of example 10, wherein thesecond data banks includes a second data bank having 8 addresses eachhaving a data width of 1 byte, the second data bank configured to store64 bits.

Example 14 includes the victim cache system of example 10, wherein arespective one of the first data banks is coupled to a respective one ofthe second data banks.

Example 15 includes a method to identify a cache hit in a victim cache,the method comprising receiving a first read address from a firstinterface of a processor, receiving a second read address from a secondinterface of the processor, comparing the first read address and thesecond read address to data banks of a multi-bank victim cache tagmemory, in response to mapping at least one of the first read address orthe second read address to a first data bank of the data banks,identifying a cache hit, and outputting a cache hit addressrepresentative of a victim cache address of cache data stored in thevictim cache.

Example 16 includes the method of example 15, wherein the firstinterface is a scalar interface and the second interface is a vectorinterface.

Example 17 includes the method of example 15, further including inresponse to identifying the cache hit, comparing the cache hit addressto a first address received from a finite-state machine associated withthe first interface, the first address representative of an addresswritten to in the victim cache in a previous pipeline stage, and inresponse to the cache hit address matching the first address, convertingthe cache hit to a cache miss.

Example 18 includes the method of example 15, further including inresponse to identifying the cache hit, comparing the cache hit addressto a first address received from a finite-state machine associated withthe second interface, the first address representative of an addresswritten to in the victim cache in a previous pipeline stage, and inresponse to the cache hit address matching the first address, convertingthe cache hit to a cache miss.

Example 19 includes the method of example 15, further including inresponse to not mapping at least one of the first read address or thesecond read address to any of the data banks, identifying a cache miss,comparing the first read address to a first address received from afinite-state machine associated with the first interface, the firstaddress representative of an address written to in the victim cache in asubsequent pipeline stage, and in response to the first read addressmatching the first address, converting the cache miss to the cache hit.

Example 20 includes the method of example 15, further including inresponse to not mapping at least one of the first read address or thesecond read address to any of the data banks, identifying a cache miss,comparing the second read address to a first address received from afinite-state machine associated with the second interface, the firstaddress representative of an address written to in the victim cache in asubsequent pipeline stage, and in response to the second read addressmatching the first address, converting the cache miss to the cache hit.

Example 21 includes the method of example 15, wherein comparing thefirst read address and the second read address to the data banks of themulti-bank victim cache tag memory is executed substantially inparallel.

Methods and Apparatus for Allocation in a Victim Cache System

Data cache architectures including a victim cache system enable the maincache (e.g., the main storage 214) to allocate data to a victim cache(e.g., the victim storage 218) when the main cache needs to create avictim. For example, when an incoming instruction is a read-miss, themain cache needs to make room for data of the read-miss. The main cachemay be a direct mapped cache such that the read-miss can only be storedin one location, indicated by the address of the read-miss. The maincache may allocate data of the read-miss location to be moved to thevictim cache when the data is dirty and evict data of the read-misslocation to be sent out to higher level memory locations when the dataof the location is clean. For example, the main cache controller mayelect a modified (e.g., dirty) line in the main storage to be victimizedand an unmodified (e.g., clean) line in the main storage to be evicted.A dirty and/or modified line of data is data that has been updated bythe CPU 102. For example, when the cache line in the main storage 214 ispresent only in the current state and has been modified from the valuein the main memory (e.g., so that a read of the data in extended memory106 is flagged or permitted because it is not up-to-date or valid), thecache line is dirty and/or modified and therefore is a candidate forallocation (e.g., victimization). The example MESI RAM 300 stores and/ortracks the cache line states (e.g., clean, dirty, shared, exclusive,etc.), therefore allowing and/or enabling the identification of dirtylines in the main storage 214.

An allocation policy of the main storage may instruct the main cachecontroller to elect to victimize a modified line because the data forthe memory address is not located in higher level cache or is located inhigher level cache but is outdated. Such an allocation policy mayinstruct the main cache controller to not allocate/victimize a cleanand/or shared line in the main storage because that line includes dataat the memory address that is already located in the higher level cache(e.g., L2 cache, L3 cache, extended memory, etc.).

However, such an allocation policy creates latency (e.g., increased thetime it would take for the CPU to retrieve the requested data) when onlyallocating dirty and/or modified lines in the L1 cache 110. The latencyis a result of using extra clock cycles to retrieve from higher levelmemory. For example, due to the parallel connection of the main storage214 and the victim storage 218, retrieving data from the higher levelmemories takes more time than retrieving data from the victim storage218.

In examples disclosed herein, the allocation policy reduces the latencyof allocating cache lines from the main cache (e.g., the main storage214) to the victim cache (e.g., the victim storage 218). For example,due to the architecture of the L1 cache 110 (e.g., the parallelconnection between the main storage 214 and the victim storage 218), theallocation policy enables the main cache controller 222 to allocate anycache line (e.g., clean and/or dirty) in the main storage 214 to thevictim storage 218. The configuring of the main storage 214 and thevictim storage 218 in parallel enables the victim storage 218 to act asan extension of the main storage 214. Thus, in addition to providing alocation to store victim lines, the victim storage 218 can also provideextra associativity to the main storage 214 by moving any cache line(e.g., clean and/or dirty) from the main storage 214 to the victimstorage 214. For example, because the victim storage 218 and mainstorage 214 are accessed in parallel (e.g., at the same time) by the CPU102, if a clean line was to be accessed and it was allocated to thevictim storage 218, the latency for accessing the clean line of datawould not be effected.

In an example operation, the main cache controller 222 obtains aninstruction (e.g., a memory operation) from the CPU interface 202 (e.g.,the scalar interface 502 and/or the vector interface 504). The maincache controller 222 obtains results from the main tag RAM access 204corresponding to the instruction. For example, the main tag RAM access204 determines if the address in the instruction matches an address inthe tag RAM 208 and provides the results to the main cache controller222. In some examples, the main cache controller 222 determines that themain storage 214 is to victimize and/or allocate data to the victimstorage 218 based on the instruction and the results from the main tagRAM access 204. For example, the main cache controller 222 determines ifthe instruction is a read operation and if the read operation is a miss(e.g., determined based on the main tag RAM access 204 results). If theread operation is a miss, the main cache controller 222 determines thatthe main storage 214 needs to allocate the line, way, block, slot, etc.of data for allocation in the victim storage 218.

In some examples, the main cache controller 222 allocates the linecorresponding to the address of the read-miss operation. For example, ifa read operation wants to read data from Address A but the main storage214 stores different data for that address location (e.g., Address A′),the main cache controller 222 has to remove the data of Address A′because the data of Address A can only be stored in one location (e.g.,Address A) of the main storage 214. The main cache controller 222identifies the location in the direct mapped cache (e.g., the mainstorage 214) that is mapped to Address A′ and allocates data of AddressA′ to the victim storage 218. Therefore, the read operation can storedata of Address A in the main storage 214.

Example methods, apparatus, systems, and articles of manufacture forallocation of data are disclosed herein. Further examples andcombinations thereof include the following:

Example 1 includes an apparatus comprising a first cache storage, asecond cache storage, a cache controller coupled to the first cachestorage and the second cache storage and operable to receive a memoryoperation that specifies an address, determine, based on the address,that the memory operation evicts a first set of data from the firstcache storage, determine that the first set of data is unmodifiedrelative to an extended memory, and cause the first set of data to bestored in the second cache storage.

Example 2 includes the apparatus of example 1, wherein the cachecontroller is to identify a portion in the first cache storagecorresponding to a directly mapped location of the address.

Example 3 includes the apparatus of example 1, wherein the cachecontroller is to allocate the first set of data to the second cachestorage to create space for data of a second memory operation.

Example 4 includes the apparatus of example 1, wherein the cachecontroller is to receive a second memory operation that specifies asecond address, determine, based on the second address, that the secondmemory operation evicts a second set of data from the first cachestorage, determine that the second set of data is modified relative toan extended memory, and cause the second set of data to be stored in thesecond cache storage.

Example 5 includes the apparatus of example 1, wherein the cachecontroller is to perform an outstanding transaction of a store queue onthe first set of data during the eviction.

Example 6 includes the apparatus of example 1, wherein the second cachestorage is to provide associativity to the first cache storage when thesecond cache storage stores the first set of data.

Example 7 includes the apparatus of example 1, wherein the second cachestorage is a victim cache storage.

Example 8 includes a method comprising receiving a memory operation thatspecifies an address, determining, based on the address, that the memoryoperation evicts a first set of data from a first cache storage,determining that the first set of data is unmodified relative to anextended memory, and cause the first set of data to be stored in asecond cache storage.

Example 9 includes the method of example 8, further includingidentifying a portion in the first cache storage corresponding to adirectly mapped location of the address.

Example 10 includes the method of example 8, further includingallocating the first set of data to the second cache storage to createspace for data of a second memory operation.

Example 11 includes the method of example 8, further including receivinga second memory operation that specifies a second address, determining,based on the second address, that the second memory operation evicts asecond set of data from the first cache storage, determining that thesecond set of data is modified relative to an extended memory, andcausing the second set of data to be stored in the second cache storage.

Example 12 includes the method of example 8, further includingperforming an outstanding transaction of a store queue on the first setof data during the eviction.

Example 13 includes the method of example 8, wherein storing the firstset of data allocated from the first cache storage includes providingassociativity to the first cache storage.

Example 14 includes the method of example 8, wherein the second cachestorage is a victim cache storage.

Example 15 includes a system comprising a central processing unit tooutput a memory operation that specifies an address, and a cache coupledto the central processing unit, the cache operable to obtain the memoryoperation from the central processing unit, the cache further includinga first cache storage, a second cache storage, and a cache controller todetermine, based on the address of the memory operation, that the memoryoperation evicts a first set of data from the first cache storage,determine that the first set of data is unmodified relative to anextended memory, and cause the first set of data to be stored in thesecond cache storage.

Example 16 includes the system of example 15, wherein the cache furtherincludes a first tag random access memory coupled to the centralprocessing unit, the first cache storage, and the cache controller, anda second tag random access memory coupled to the central processingunit, the second cache storage, and the cache controller.

Example 17 includes the system of example 15, wherein the cachecontroller is to determine, based on a second address of a second memoryoperation, that the second memory operation evicts a second set of datafrom the first cache storage, determine that the second set of data ismodified relative to an extended memory, and cause the second set ofdata to be stored in the second cache storage.

Example 18 includes the system of example 15, wherein the cachecontroller is to perform an outstanding transaction of a store queue onthe first set of data during the eviction.

Example 19 includes the system of example 15, wherein the first cachestorage and the second cache storage are connected in parallel to thecentral processing unit.

Example 20 includes the system of example 15, wherein the first cachestorage is a direct mapped cache and the second cache storage is a fullyassociative cache, the direct mapped cache coupled and the fullyassociative cache coupled to the central processing unit in parallel.

Methods and Apparatus to Facilitate Read-Modify-Write Support in aCoherent Victim Cache with Parallel Data Paths

To facilitate a memory system that operates with memory coherence, thatis, to facilitate a memory system in which corresponding memorylocations for each processing element contain the same stored data, someexample systems are prevented from including a victim storage. Examplesdisclosed herein overcome this challenge by facilitating a fullycoherent memory system in which the victim storage (e.g., the victimstorage 218) can operate in memory coherence operations in the system.

To provide coherency on the data cache 108, the example scalar interface502 (e.g., a sixty-four-bit wide interface) and the example vectorinterface 504 (e.g., a five hundred and twelve-bit wide interface) areincluded in the victim storage 218 of the L1 cache 110. In this manner,the victim storage 218 of the L1 cache 110 is capable of servicing twodata paths from the CPU 102.

In some examples disclosed herein, the snoop address component 506 isutilized to store the MESI state of every cache line in the victimstorage 218 in the MESI RAM 300. By storing the MESI state of everycache line in the MESI RAM 300, the victim cache system supportscoherency.

Additionally, the example snoop address component 506 obtains an examplesnoop request from a higher-level memory cache memory (e.g., the L2 datacache 112) and is transmits such a snoop request to the tag RAM 210 andcomparison logic 306 c. In some examples, the snoop address component506 triggers an address read instruction to the tag RAM 210. Forexample, when the L2 data cache 112 is unable to identify data requestedin a read request from the CPU 102, the L2 data cache 112 transmits thesnoop address component 506 to the lower level, L1 data cache 110 toattempt to execute a read request of a memory address in the tag RAM210. Additionally, the snoop address component 506 provides the addressread to the comparison logic 306 c. In the event a miss is identified(e.g., the read issued to the tag RAM 210 returns a miss), anappropriate snoop response indicating that a read was unsuccessful isgenerated and transmitted to the higher-level data cache that generatedthe snoop address component 506 (e.g., the L2 data cache 112).

Alternatively, in the event a hit is identified (e.g., the read issuedto the tag RAM 210 returns a hit), the state of the corresponding linein the MESI RAM 300 is read and the example address encoder 326 cgenerates an address value for use by the victim storage 218 inobtaining the data. Accordingly, an appropriate response indicating thatthe read request was successful is generated and transmitted back to thehigher-level data cache that generated the snoop address component 506(e.g., the L2 data cache 112) as the snoop response. In examplesdisclosed herein, the snoop response includes the data in the victimstorage 218 corresponding to the address in the tag RAM 210.

In an example operation, the corresponding store queue (e.g., the victimcache store queue 216) may be processing a write instruction to theaddress that is being read via the snoop address. Accordingly, while thevictim storage 218 is servicing a snoop request (e.g., while the snooprequest is being processed in response to the snoop address component506 obtaining the snoop request), the victim cache store queue 216forwards the data from the victim cache store queue 216 (e.g., the datastored in latch 402 e) to the response multiplexer 508. In this manner,any state change obtained by the vector interface 504 due to the snoopaddress and any recently updated address obtained from the victim cachestore queue 216 is forwarded to the higher-level data cache (e.g., theL2 data cache 112).

In the topology illustrated in FIG. 5, the coherency pipeline is longerthan the victim cache pipeline to provide enough time for the victimcache controller 224 to properly order a potential snoop response and/orsubsequent CPU 102 operation in the event such a snoop response and/orsubsequent CPU 102 operation is issued to a higher level memorycontroller.

In examples disclosed herein, the victim storage 218 of the L1 datacache 110 is capable of issuing tag-updates to higher level cachecontroller in the event tracking of cache lines is requested. In thismanner, the victim storage 218 can facilitate tracking of cache lines todistinguish between exclusive and modified cache elements.

In examples disclosed herein, the victim storage 218 of the L1 datacache 110 supports global coherence operation by allowing a globalcoherence operation to process on a fully associative cache anditerating over the tag RAM 208 based on sets.

While the above-mentioned operation is described in connection with theL1 data cache 110, any of the above-mentioned operations and/or elementsmay be implemented on any of the L2 data cache 112, the L3 data cache114, and/or any additional level data cache in the data cache 108.

Example methods, apparatus, systems, and articles of manufacture tofacilitate read-modify-write support in a coherent victim cache withparallel data paths are disclosed herein. Further examples andcombinations thereof include the following:

Example 1 includes an apparatus comprising a random-access memoryconfigured to be coupled to a central processing unit via a firstinterface and a second interface, the random-access memory configured toobtain a read request indicating a first address to read via a snoopinterface, an address encoder coupled to the random-access memory, theaddress encoder to, when the random-access memory indicates a hit of theread request, generate a second address corresponding to a victim cachebased on the first address, and a multiplexer coupled to the victimcache to transmit a response including data obtained from the secondaddress of the victim cache.

Example 2 includes the apparatus of example 1, wherein the read requestis transmitted by a level two data cache.

Example 3 includes the apparatus of example 1, wherein the multiplexeris configured to be coupled to a victim cache storage queue, themultiplexer to obtain input data from the victim cache storage queueindicating a value to be written to the second address.

Example 4 includes the apparatus of example 3, wherein the multiplexeris configured to transmit the response including the input data from thevictim cache storage queue.

Example 5 includes the apparatus of example 1, wherein the random-accessmemory is a tag random access memory.

Example 6 includes the apparatus of example 1, wherein the victim cacheis a multi-bank memory.

Example 7 includes the apparatus of example 1, wherein the firstinterface is a scalar interface and the second interface is a vectorinterface.

Example 8 includes the apparatus of example 7, wherein the scalarinterface is a sixty-four-bit wide interface, the vector interface is afive hundred and twelve-bit wide interface.

Example 9 includes a system comprising a controller, a first memory, asecond memory configured to obtain a snoop request from the firstmemory, the second memory to execute a read request of a random-accessmemory in response to the snoop request, when the random-access memoryindicates a hit of the read request, generate an address correspondingto a victim cache, the address to be used in reading the victim cache,and transmit a response to the second memory including data obtainedfrom the address of the victim cache.

Example 10 includes the system of example 9, wherein the first memory isa level two cache memory and the second memory is a level one cachememory.

Example 11 includes the system of example 9, wherein the second memoryincludes a multiplexer configured to be coupled to a victim cachestorage queue, the multiplexer to obtain input data from the victimcache storage queue indicating a value to be written to the address ofthe victim cache in the second memory.

Example 12 includes the system of example 11, wherein the multiplexer isconfigured to transmit the response including the input data from thevictim cache storage queue.

Example 13 includes the system of example 9, wherein the second memoryis coupled to the controller via a scalar interface and a vectorinterface, and the second memory is coupled to the first memory via asnoop interface.

Example 14 includes the system of example 13, wherein the scalarinterface is a sixty-four-bit wide interface, the vector interface is afive hundred and twelve-bit wide interface.

Example 15 includes the system of example 13, wherein the controller isa central processing unit.

Example 16 includes a method comprising obtaining a read requestindicating a first address to read via a snoop interface, when the readrequest is a hit, generate a second address corresponding to a victimcache based on the first address, and generating a response includingdata obtained from the second address of the victim cache.

Example 17 includes the method of example 16, further includingtransmitting the read request from a level two data cache.

Example 18 includes the method of example 16, further includingobtaining input data from a victim cache storage queue indicating avalue to be written to the second address.

Example 19 includes the method of example 18, further includingtransmitting the response including the input data from the victim cachestorage queue.

Example 20 includes the method of example 16, wherein the victim cacheis a multi-bank memory.

Methods and Apparatus for Eviction in Dual Datapath Victim Cache System

In a victim cache system, the main cache (e.g., the main storage 214)victimizes (e.g., allocates) cache lines to the victim cache (e.g.,victim storage 218) when the main cache needs to store new data. Whenthe main cache creates a victim, the replacement policy (e.g.,replacement policy component 308) determines where the victim can bestored in the victim cache (e.g., the victim storage 218). In someexamples, the victim cache is full and thus needs to evict data to thehigher level cache memories (e.g., L2 cache 112, L3 cache 114, extendedmemory 106). The victim cache (e.g., victim storage 218) also evictsdata to the higher level cache memories when a write-miss occurs. Forexample, the victim storage 218 includes a write-miss buffer thatbuffers write-miss data. The replacement policy may utilize fixedschemes to determine what data to evict from the victim cache. Forexample, eviction schemes such as First In First Out (FIFO) scheme,Random scheme, and Least Recently Used (LRU) scheme. However, sucheviction schemes are not configured to efficiently manage the evictionof data from the victim cache when there are two or more data paths.

For example, the FIFO scheme evicts a block of data that has been in thevictim cache for the longest time (e.g., the data in slot 0 if it is thefirst time the eviction is occurring). In a dual data path victim cachesystem (e.g., the victim cache section illustrated in FIG. 5), the FIFOscheme does not work when two incoming CPU accesses (e.g., instructions)are both misses and/or are both allocating instructions. In such anexample, if two sets from the victim cache are not speculatively lockedand read, then additional stalls are created.

In a different example, the main storage 214 stores an address A and thevictim storage 218 stores an address B. The CPU 102 sends two requests:the CPU 102 requests to read data of address A′ utilizing DP0 and theCPU 102 requests to read data from address B utilizing DP1. The data ofaddress A′ is mapped to the same location as the address A in the mainstorage 214. Therefore, the first data path DP0 needs to allocate thedata in address A to the victim storage 218 (e.g., allocate data ofaddress A′ into the main storage 214). In a regular FIFO scheme, addressA would be allocated to slot 0 of the victim storage 218. However, theslot 0 is occupied by address B and the CPU 102 is requesting to accessthe address B in parallel to requesting to allocate data of the readinstruction to address A′. Therefore, if the data path DP0 evictedaddress B from slot 0, a stall (e.g., a cycle or a number of cycles forwhich the CPU 102 is stalled waiting for the memory access) would becreated in order to retrieve the evicted data later from higher levelcaches.

Examples disclosed herein include an eviction scheme that efficientlyevicts data from the victim storage 218 in a dual data path victim cachesystem. The example eviction scheme is implemented by the replacementpolicy component 308 of FIGS. 3 and 5. For example, the replacementpolicy component 308 includes logic that analyzes inputs and produces anoutput. For example, the replacement policy component 308 obtains inputsfrom the hit-miss comparison logic 306 a and 306 b and determines whatlocation in the victim storage 218 is to be replaced by data from themain storage 214 and/or replaced by data from the write-missinstruction. In examples disclosed herein, the replacement policycomponent 308 reserves entries (e.g., ways, sets, cache lines, etc.) inthe victim storage 218 that correspond to eviction locations. Forexample, the replacement policy component 308 speculatively locks (e.g.,reserves) first and second victim cache lines (e.g., sets) that arespecifically for eviction. The first and second victim cache lines maybe locked for specific data paths (e.g., first victim cache line lockedfor DP0 and second victim cache line locked for DP1). The eviction logicimplemented by the replacement policy component 308 is described infurther detail below in connection with FIG. 6.

Turning to FIG. 6, an example first table 602 and an example secondtable 604 are depicted. The example first and second tables 602, 604describe the logic of the example replacement policy component 308. Theexample replacement policy component 308 utilizes an LRU value. As usedherein, an LRU value corresponds to a way that is the least recentlyused portion in the victim storage 218. In some examples, the LRU valuecorresponds to a location in the victim storage element 218 that has notbeen recently accessed by the first or second data path. In a fullyassociated cache (e.g., the victim storage 218), an address can bemapped to any “way” in the cache. Thus, a way is a block in the cachethat stores data and includes a tag. In some LRU schemes, when thevictim cache needs to evict data, the data in the location indicated bythe LRU value (e.g., the data in the portion not recently accessed inthe victim storage 218) is evicted. For example, in a 3-way cache, anaddress A, an address B, and an address C occupy all three ways (e.g.,blocks, slots, etc.). In this example, address A has been recentlyaccessed by the CPU 102, address B was accessed just prior to theaddress A access, and address C was accessed prior to address B.Therefore, address C is the least recently used address and the portionmapped to address C has a location equal to the LRU value.

The example first table 602 of FIG. 6 includes a first data pathscenario 606, a second data path scenario 608, and a third data pathscenario 610. The example data path scenarios 606, 608, 610 correspondto the validity of the transactions (e.g., accesses) on DP0 and DP1 ofFIG. 5. Validity of a transaction corresponds to whether the CPU 102sends valid instructions to the L1 cache 110. A valid instruction on thefirst data path DP0 and an invalid instruction on the second data pathDP1 corresponds to when the processing cores send an instruction on thefirst data path DP0 and leave the second data path DP1 idle. In someexamples, during a particular clock cycle, the first data path DP0includes invalid instructions. In some examples, during a particularclock cycle, the second data path DP1 includes invalid instructions.Additionally and/or alternatively, both the data paths DP0 and DP1 caninclude valid instructions and/or can include invalid instructions.

In the example first table 602, the first data path scenario 606corresponds to when both data paths (DP0, DP1) of FIG. 5 include validtransactions (DP0_valid=1, DP1_valid=1) in the same clock cycle. In someexamples, the replacement policy component 308 obtains results and/orinstructions from both data paths DP0, DP1.

In the example first table 602, the second data path scenario 608corresponds to the first data path (DP0) including a valid transaction(DP0_valid=1) and the second data path (DP1) including an invalidtransaction (DP1_valid=0). In such an example, the replacement policycomponent 308 determines that the transaction of DP1 includes invalidinstructions.

In the example first table 602, the third data path scenario 610corresponds to the first data path (DP0) including an invalidtransaction (DP0_valid=0) and the second data path (DP1) including avalid transaction (DP1_valid=1). In some examples, the replacementpolicy component 308 determines that that transaction of DP0 is includesinvalid instructions.

The example first data path scenario 606 in the example first table 602includes an example hit-hit action 612, an example miss-hit action 614,an example hit-miss action 616, and an example miss-miss action 618. Theexample hit-hit action 612 is indicative that the address on DP0 and theaddress on DP1 hit (e.g., matches) an address in either of the tag RAMs208, 210. In other words, the example hit-hit action 612 is indicativethat the address on DP0 and the address on DP1 hit an address in mainstorage 214, the victim storage 218 and/or the write miss cache(described above in connection with FIGS. 3A-3D). The example miss-hitaction 614 is indicative that the address on DP0 does not match anaddress in main storage 214, the victim storage 218, and/or the writemiss cache and that the address on DP1 hits an address in the mainstorage 214, the victim storage 218 and/or the write miss cache. In someexamples, the miss portion of the miss-hit action 614 is indicative thatDP0 is to allocate a cache line from the main storage 214 to the victimstorage 218 and thus, is evicting data from the victim storage 218 tomake room for the cache line of the main storage 214. The examplehit-miss action 616 is indicative that the address on DP0 hits anaddress in the victim storage 218 and/or the write miss cache and thatthe address on DP1 does not match an address in the victim storage 218and/or the write miss cache. In some examples, the miss portion of thehit-miss action 616 is indicative that DP1 is to allocate a cache linefrom the main storage 214 to the victim storage 218 and thus, isevicting data from the victim storage 218 to make room for the cacheline of the main storage 214. The example miss-miss action 618 isindicative that the addresses of DP0 and DP1 both do not have a match inthe victim storage 218 and/or the write miss cache. In some examples,the miss-miss action 618 is indicative that both data paths DP0 and DP1are to allocate data from the main storage 214 to the victim storage218. Additionally and/or alternatively, a miss is indicative that awrite-miss is to write data to the write-miss buffer in the victimstorage 218.

The example second data path scenario 608 in the example first table 602includes an example DP0 hit action 620 and an example DP0 miss action622. In the second data path scenario 608, the first data path DP0includes a valid transaction and the second data path DP1 includes aninvalid transaction. In some examples, the replacement policy component308 disregards the second data path DP1 because the second data path DP1does not include instructions.

The example third data path scenario 610 in the example first table 602includes an example DP1 hit action 624 and an example DP1 miss action626. The example DP1 hit action 624 corresponds to the action thereplacement policy component 308 takes when the address of the seconddata path DP1 matches an address in the victim storage 218 and/or thewrite miss cache. The example DP1 miss action 624 corresponds to theaction the replacement policy component 308 takes when the address ofthe second data path DP1 does not match an address in the victim storage218 and/or the write miss cache. Similarly to the example DP0 hit action620 and the DP0 miss action 622 under the example second data pathscenario 608, the example replacement policy component 308 disregardsthe transaction of the first data path DP0 in the example third datapath scenario 610 because the transaction is invalid.

In the example first table 602, DP0 Hit Way indicates a portion of thevictim storage 218 and/or the write miss cache that should be accessed(e.g., read from, evicted, written to, etc.) by the first data path DP0when the instruction is a hit. In the example first table 602, DP1 HitWay is a portion in the victim storage 218 and/or the write miss cachethat should be accessed by the second data path DP1 when theinstructions is a hit.

In the example first table 602, the variable ‘Y’ is the variable thatindicates the location of the current way selected as the LRU andindicates where the first data path DP0 should remove data from. In someexamples, Y is assigned to the DP0 pointer. For example, when DP0 needsto evict a portion in the victim storage 218, then DP0 pointer points tothe location Y (e.g., the LRU way) for eviction. In some examples, thereplacement policy component 308 is to store an indicator of the LRU wayof the victim storage 218 to be replaced by DP0. For example, thereplacement policy component 308 keeps an indicator, that can beaccessed by the cache controller 220, that a particular way, notrecently accessed, is available for eviction by the first data path DP0.As used herein, the terms “pointer” and “indicator” may be usedinterchangeably.

In the example first table 602, the variable ‘Y+1’ indicates thelocation of the next LRU way where the second data path DP1 shouldremove data from. In some examples, ‘Y+1’ is assigned to the DP1pointer. For example, when the second data path DP1 needs to evict aportion in the victim storage 218, the DP1 pointer points to thelocation Y+1 (e.g., the next LRU way) for eviction. In some examples,the replacement policy component 308 is to store an indicator of the LRUway of the victim storage 218 to be replaced by DP1. For example, thereplacement policy component 308 keeps an indicator, that can beaccessed by the cache controller 220, that a particular way, notrecently accessed, is available for eviction by the first data path DP0.

In a first example operation of the replacement policy component 308,both data paths (DP0 and DP1) include valid transactions (e.g.,indicated in first data path scenario 606) and both data paths (DP0 andDP1) include addresses that match addresses in the example victimstorage element 218 (e.g., the hit-hit action 612). For example, thecomparison logic 306 a and 306 b compares the addresses of DP0 and DP1to addresses in the example tag RAM 210 and provides a hit result to thereplacement policy component 308. Since both data paths are valid andboth data paths are hits, the DP0 Hit Way points to the portion (e.g.,the way) in the victim storage 218 that includes hit/matching datacorresponding to data path DP0 and DP1 Hit Way points to the way thatincludes the hit/matching data corresponding to data path DP1. Thevictim storage 218 responds with the requested data. The location of theLRU way does not increment and remains at location Y.

In a second example operation of the replacement policy component 308,both data paths (DP0 and DP1) include valid transactions (e.g.,indicated in first data path scenario 606), the first data path DP0 is amiss, and the second data path DP1 hits the victim storage 218 (e.g.,the miss-hit action 614). For example, the first comparison logic 306 areturns a “miss” result to the replacement policy component 308 and thesecond comparison logic 306 b returns a “hit” result to the replacementpolicy component 308. The DP1 Hit Way points to the portion (e.g., way)in the victim storage 218 that includes the hit/matching data (e.g., thehit way). In some examples, the first data path DP0 is to evict datafrom a portion (e.g., way) in the victim storage 218. Therefore, the DP0pointer points to the location Y in the victim storage 218 that is to beevicted.

Before eviction occurs, the replacement policy component 308 determinesif the DP1 Hit Way matches the address of the LRU way (e.g., locationY). If the DP1 Hit Way does not have the same location as Y, the DP0pointer points to the way having a location equal to the location Y(e.g., the LRU way). If the DP1 Hit Way does match the address of theLRU way, the DP0 pointer points to the location of the DP1 pointer (Y+1)so that the DP0 can evict data without conflicting with DP1 Hit Way.

In the second example scenario 614, the LRU value and the next LRU valueare incremented based on which location was evicted. For example, if DP0evicted data from location Y+1 (e.g., the DP1 Hit Way matches thelocation of the DP0 pointer), the LRU value is incremented twice and thenext LRU value is incremented twice. Otherwise, if DP0 evicted data fromlocation Y (e.g., DP1 Hit Way did not match the location of DP0 pointer)the LRU value is incremented once and the next LRU value is incrementedonce.

In a third example operation of the replacement policy component 308,both data paths (DP0 and DP1) include valid transactions (e.g.,indicated in first data path scenario 606), the first data path DP0 is ahit, and the second data path DP1 is a miss (e.g., the hit-miss action616). For example, the first comparison logic 306 a returns a “hit”result to the replacement policy component 308 and the second comparisonlogic 306 b returns a “miss” result to the replacement policy component308. The DP0 Hit Way points to the way in the victim storage 218 thatincludes the hit/matching data. In some examples, the miss causes thesecond data path DP1 to evict a way to make room in the victim storage218. Therefore, the DP1 pointer points to location Y+1 in the victimstorage 218 that is to be evicted.

Before eviction occurs, the replacement policy component 308 determinesif the DP0 Hit Way matches the address of the next LRU way (e.g.,location Y+1). If the replacement policy component 308 determines theDP0 Hit Way matches the address of the next LRU way (e.g., Y+1), the DP1pointer points to the location of the DP0 pointer (e.g., location Y) sothat the DP1 can evict data without conflicting with DP0 Hit Way. If theDP0 Hit Way does not match the address of the next LRU way, then the DP1evicts data from location Y+1.

In the third example scenario 616, the LRU value and the next LRU valueare incremented based on which location was evicted. For example, if DP1evicted data from location Y (e.g., the DP0 Hit Way matches the locationof the DP1 pointer), the LRU value is incremented once and the next LRUvalue is incremented once. Otherwise, if DP1 evicted data from locationY+1 (e.g., DP0 Hit Way did not match the location of DP1 pointer) theLRU value is incremented twice and the next LRU value is incrementedtwice.

In a fourth example operation of the replacement policy component 308,both data paths (DP0 and DP1) include valid transactions (e.g.,indicated in first data path scenario 606) and both data paths areflagged as misses (e.g., column 618). For example, the comparison logic306 a and 306 b returns “miss” results to the replacement policycomponent 308 when both addresses in the data paths DP0 and DP1 are notfound and/or matched with the addresses in the tag RAMs 208, 210. In thefourth operation, both data paths DP0 and DP1 are to evict ways in thevictim storage 218. Therefore, DP0 pointer points to location Y and DP1pointer points to location Y+1.

When both eviction operations are complete, the LRU value is incrementedby two (e.g., Y+2) and the next LRU value is incremented by two (e.g.,(Y+1)+2). In a subsequent operation, if DP0 and DP1 are misses, DP0 Waypoints to the new LRU value (e.g., Y+2) and DP1 Way points to the nextLRU value (e.g., (Y+1)+2).

In a fifth example operation of the replacement policy component 308,the first data path DP0 is a valid transaction and the second data pathDP1 is an invalid transaction (e.g., indicated in second data pathscenario 608). In the fifth example operation, the first data path DP0is a hit (e.g., indicated in the DP0 hit action 620). For example, thecomparison logic 306 a returns a “hit” result to the replacement policycomponent 308. The DP0 Hit Way points to the way in the victim storage218 that includes the matching data. The LRU value (Y) remains the samebecause no data is to be evicted in the clock cycle.

In a sixth example operation of the replacement policy component 308,the first data path DP0 is a valid transaction and the second data pathDP1 is an invalid transaction (e.g., indicated in second data pathscenario 608). In the sixth example operation, the first data path DP0is a miss (e.g., indicated in the DP0 miss action 622). For example, thecomparison logic 306 a returns a “miss” result to the replacement policycomponent 308. In this example, the first data path DP0 is to evict datafrom the victim storage 218. The example DP0 pointer points to thelocation Y (e.g., the LRU way). After eviction, the LRU value isincremented (e.g., Y+1).

In a seventh example operation of the replacement policy component 308,the first data path DP0 is an invalid transaction and the second datapath DP1 is a valid transaction (e.g., indicated in third data pathscenario 610). In the seventh example operation, the second data pathDP1 is a hit (e.g., indicated in the DP1 hit action 624). For example,the comparison logic 306 b returns a “hit” result to the replacementpolicy component 308. The DP1 Hit Way points to the way in the victimstorage 218 that includes the matching data. The LRU value (Y) remainsthe same because no data is to be evicted in the clock cycle.

In an eighth example operation of the replacement policy component 308,the first data path DP0 is an invalid transaction and the second datapath DP1 is a valid transaction (e.g., indicated in third data pathscenario 610). In the eighth example operation, the second data path DP1is a miss (e.g., indicated in the DP1 miss action 626). For example, thecomparison logic 306 b returns a “miss” result to the replacement policycomponent 308. In this example, the second data path DP1 is to evictdata from the victim storage 218. The DP1 pointer points to the locationY (e.g., the LRU way). The DP1 pointer does not point to location Y+1because of the invalid transaction of DP0. Otherwise, when bothtransactions are valid, DP1 always points to Y+1 (e.g., unless switchedwhen DP0 Hit Way matches Y+1). After the second data path DP1 evicts thedata from location Y, the LRU value is incremented (e.g., Y+1).

Turning to the second table 604, second table 604 illustrates theincrementation of the LRU value when the first data path DP0 and/or thesecond data path DP1 is allocating data into the victim storage 218. Forexample, when a read-miss occurs, the main storage 214 allocates a lineof data to the victim storage 218 utilizing one of the data paths. Thesecond table 604 includes a first valid column 626, a second validcolumn 628, a first allocate column 630, a second allocate column 632, afirst LRU interference 634, a second LRU interference 636, and an LRUincrement column 638.

In the second table 604, the example first valid column 626 correspondsto the validity of the second data path transaction. For example, a zero(0) indicates the DP1 transaction is invalid and a one (1) indicatesthat the DP1 transaction is valid. The example second valid column 628corresponds to the validity of the first data path transaction. Forexample, a zero (0) indicates the DP0 transaction is invalid and a one(1) indicates that the DP0 transaction is valid.

In the second table 604, the example first allocate column 630 indicatesthe allocation status of the second data path DP1. The allocation statuscorresponds to allocation of data from the main storage 214 to thevictim storage 218 in a clock cycle. For example, a zero (0) indicatesthat the second data path DP1 is not allocating data into the victimstorage 218 and a one (1) indicates that the second data path DP1 isallocating data into the victim storage 218. The example second allocatecolumn 632 indicates the allocation status of the first data path DP0.For example, a zero (0) indicates that the first data path DP0 is notallocating data into the victim storage 218 and a one (1) indicates thatthe first data path DP0 is allocating data into the victim storage 218.When a data path is allocating data into the victim storage 218, thedata path evicts a way (e.g., slot, block, etc.) to make room for thedata being allocated. In some examples, data is allocated to the victimstorage 218 when a read-miss occurs in the main storage 214.

In the second table 604, the first LRU interference column 634 indicateswhether the first data path DP0 hits the same location in the victimstorage 218 as the location of the second data path allocate pointer.For example, the address of the first data path DP0 is located in theleast recently used location of the victim storage 218. The first LRUinterference column 634 includes a one (1) to indicate that the firstdata path DP1 hit location equals the location of the second data pathDP1 allocate pointer.

The second LRU interference column 636 indicates whether the second datapath DP1 hits the same location in the victim storage 218 as thelocation of the second data path allocate pointer. For example, theaddress of the second data path DP1 is located in the least recentlyused location of the victim storage 218. The second LRU interferencecolumn 636 includes a one (1) to indicate that the second data path DP1hit location equals the location of the first data path allocatepointer. As used herein, the first data path allocate pointer points tothe location Y (LRU value) when DP0 is to allocate and the second datapath allocate pointer points to the location Y+1 (next LRU value) whenthe DP1 is to allocate. In some examples, the pointers notify the cachecontroller 220 to evict a portion of the victim storage 218 to thehigher level caches (e.g., L2 112, L3 114, extended memory 106). Theexample replacement policy component 308 may initialize the first datapath allocate pointer to point to location Y (LRU portion) andinitialize the second data path allocate pointer to point to Y+1 (nextLRU portion).

In the second table 604, the LRU increment column 628 indicates theincrementation of the LRU value, Y. For example, the replacement policycomponent 308 increments the LRU value by one (e.g., Y+1), by two (e.g.,Y+2), or by nothing (e.g., Y). In some examples, the incrementation ofthe LRU value depends on the status of the data paths DP0 and DP1.

In an example operation, both the first data path DP0 and the seconddata path DP1 include valid transactions. The example replacement policycomponent 308 determines if any of the data paths are allocating. Forexample, the cache controller 220 sends information to the replacementpolicy component 308 when the main storage 214 needs to allocate data.

If the first data path DP0 is allocating data (e.g., moving data fromthe main storage 214 to the victim storage 218), the first data path DP0evicts data (e.g., indicated by the first data path allocate pointer)from the victim storage 214. To evict data, the replacement policycomponent 308 determines whether the second data path DP1 was a hit andwhere the hit location is. For example, the replacement policy component308 analyzes the location of the address of the second data path DP1 anddetermines if that location matches the location of the first data pathallocate pointer.

If the second data path hit location is equal to the location of thefirst data path allocate pointer (e.g., DP1 hit location=Y), thereplacement policy component 308 updates the first data path allocatepointer to point to the next LRU value (Y+1) (e.g., notifies the cachecontroller 220 to evict data of next LRU value). In this manner, thesecond data path DP1 reads/writes from the hit location Y and the firstdata path DP0 evicts data of the LRU location Y+1. By way of thisoperation, the first data path DP0 does not evict the read/write data ofDP1. After the eviction has occurred (e.g., eviction of data from Y+1 inthe victim storage 218), the replacement policy component 308 incrementsthe first data path allocate pointer by two and the second data pathallocate pointer by two. For example, the replacement policy component308 increments LRU value (Y) by two and the next LRU value (Y+1) by twobecause DP0 just evicted location Y+1, and therefore, the new LRU valuewill be Y+2. This operation is illustrated at row 640.

If the second data path hit location is not equal to the location of thefirst data path allocated pointer (e.g., DP1 hit location does not equalY), the replacement policy component 308 notifies the cache controller220 that location Y is to be evicted. In this manner, the cachecontroller 220 evicts data from the location Y in the victim storage218. After eviction has occurred (e.g., eviction of data from Y in thevictim storage 218), the replacement policy component 308 increments thefirst data path allocate pointer by one and the second data pathallocate pointer by one. For example, the replacement policy component308 increments LRU value (Y) by one and the next LRU value (Y+1) by onebecause DP0 just evicted location Y, and therefore, the new LRU valuewill be Y+1. This operation is illustrated at row 642.

In a different operation, the second data path DP1 is allocating data(e.g., moving data from the main storage 214 to the victim storage) andthe second data path DP1 evicts data (e.g., indicated by the second datapath allocate pointer) from the victim storage 214. To evict data, thereplacement policy component 308 determines whether the first data pathDP0 was a hit and where the hit location is. For example, thereplacement policy component 308 analyzes the location of the address ofthe first data path DP0 and determines if that location matches thelocation of the second data path allocate pointer.

If the first data path hit location is equal to the location of thesecond data path allocate pointer (e.g., DP0 hit location=Y+1), thereplacement policy component 308 updates the second data path allocatepointer to point to the LRU value (Y) (e.g., notifies the cachecontroller 220 to evict data of LRU value). In this manner, the firstdata path DP0 reads/writes from the hit location Y+1 and the second datapath DP1 evicts data of the LRU location Y. By way of this operation,the second data path DP1 does not evict the read/write data of DP0.After the eviction has occurred (e.g., eviction of data from Y in thevictim storage 218), the replacement policy component 308 increments thefirst data path allocate pointer by one and the second data pathallocate pointer by one. For example, the replacement policy component308 increments LRU value (Y) by one and the next LRU value (Y+1) by onebecause DP1 just evicted location Y, and therefore, the new LRU valuewill be Y+1. This operation is illustrated at row 644.

If the first data path hit location is not equal to the location of thesecond data path allocated pointer (e.g., DP0 hit location does notequal Y+1), the replacement policy component 308 notifies the cachecontroller 220 that location Y+1 is to be evicted. In this manner, thecache controller 220 evicts data from the location Y+1 in the victimstorage 218. After eviction has occurred (e.g., eviction of data fromY+1 in the victim storage 218), the replacement policy component 308increments the first data path allocate pointer by two and the seconddata path allocate pointer by two. For example, the replacement policycomponent 308 increments the LRU value (Y) by two and the next LRU value(Y+1) by two because DP1 just evicted location Y+1, and therefore, thenew LRU value will be Y+2. This operation is illustrated at row 646.

Example methods, apparatus, systems, and articles of manufacture foreviction in a victim storage are disclosed herein. Further examples andcombinations thereof include the following:

Example 1 includes an apparatus comprising a cache storage, a cachecontroller operable to receive a first memory operation and a secondmemory operation concurrently, comparison logic operable to identify ifthe first and second memory operations missed in the cache storage, anda replacement policy component operable to, when at least one of thefirst and second memory operations corresponds to a miss in the cachestorage, reserve an entry in the cache storage to evict based on thefirst and second memory operations.

Example 2 includes the apparatus of example 1, wherein the replacementpolicy component is to speculatively lock the entry in the cache storagefor eviction.

Example 3 includes the apparatus of example 1, wherein the replacementpolicy component is operable to store an indicator of a first way of thecache storage to be replaced, in response to the first memory operationmissing in the cache storage and the second memory operation hitting inthe cache storage determine whether the second memory operation isdirected to the first way of the cache storage indicated by theindicator, and increment the indicator to indicate a second way of thecache storage based on the second memory operation being directed to thefirst way of the cache storage, and causing the second way of the cachestorage to be evicted based on the first memory operation and theincremented indicator.

Example 4 includes the apparatus of example 1, wherein the replacementpolicy component is operable to store an indicator of a second way ofthe cache storage to be replaced, in response to the second memoryoperation missing in the cache storage and the first memory operationhitting in the cache storage determine whether the first memoryoperation is directed to the second way of the cache storage indicatedby the indicator, and decrement the indicator to indicate a first way ofthe cache storage based on the first memory operation being directed tothe second way of the cache storage, and causing the first way of thecache storage to be evicted based on the second memory operation and theincremented indicator.

Example 5 includes the apparatus of example 1, wherein the replacementpolicy component is operable to store a first indicator of a first wayand a second indicator of a second way of the cache storage to bereplaced, in response to the first memory operation missing in the cachestorage and the second memory operation missing in the cache storagecausing the first way of the cache storage to be evicted based on thefirst memory operation and the second way of the cache storage to beevicted based on the second memory operation.

Example 6 includes the apparatus of example 5, wherein the replacementpolicy component is operable to increment the first indicator by twolocations and the second indicator by two locations after the first wayand the second way of the cache storage are evicted.

Example 7 includes the apparatus of example 1, wherein the cache storageis a victim cache storage.

Example 8 includes the apparatus of example 1, further including a firstinterface and a second interface, the first interface to obtain thefirst memory operation from a central processing unit and the secondinterface to obtain the second memory operation from the centralprocessing unit, the first interface and the second interface coupled tothe comparison logic and the cache controller.

Example 9 includes the apparatus of example 8, wherein the firstinterface is a vector interface and the second interface is a scalarinterface.

Example 10 includes a method comprising receiving a first memoryoperation and a second memory operation concurrently, identifying if thefirst and second memory operations missed in a cache storage, and whenat least one of the first and second memory operations corresponds to amiss in the cache storage, reserving an entry in the cache storage toevict based on the first and second memory operations.

Example 11 includes the method of example 10, further includingspeculatively locking the entry in the cache storage for eviction.

Example 12 includes the method of example 10, further including storingan indicator of a first way of the cache storage to be replaced, inresponse to the first memory operation missing in the cache storage andthe second memory operation hitting in the cache storage determiningwhether the second memory operation is directed to the first way of thecache storage indicated by the indicator, and incrementing the indicatorto indicate a second way of the cache storage based on the second memoryoperation being directed to the first way of the cache storage, andcausing the second way of the cache storage to be evicted based on thefirst memory operation and the incremented indicator.

Example 13 includes the method of example 10, further including storingan indicator of a second way of the cache storage to be replaced, inresponse to the second memory operation missing in the cache storage andthe first memory operation hitting in the cache storage determiningwhether the first memory operation is directed to the second way of thecache storage indicated by the indicator, and decrementing the indicatorto indicate a first way of the cache storage based on the first memoryoperation being directed to the second way of the cache storage, andcausing the first way of the cache storage to be evicted based on thesecond memory operation and the incremented indicator.

Example 14 includes the method of example 10, further including storinga first indicator of a first way and a second indicator of a second wayof the cache storage to be replaced, in response to the first memoryoperation missing in the cache storage and the second memory operationmissing in the cache storage causing the first way of the cache storageto be evicted based on the first memory operation and the second way ofthe cache storage to be evicted based on the second memory operation.

Example 15 includes the method of example 14, further includingincrementing the first indicator by two locations and the secondindicator by two locations after the first way and the second way of thecache storage are evicted.

Example 16 includes a system comprising a central processing unit toconcurrently output a first memory operation and a second memoryoperation, a cache coupled to the central processing unit, the cachefurther including a cache storage, a cache controller operable toreceive a first memory operation and a second memory operationconcurrently, comparison logic operable to identify if the first andsecond memory operations missed in the cache storage, and a replacementpolicy component operable to, when at least one of the first and secondmemory operations corresponds to a miss in the cache storage, reserve anentry in the cache storage to evict based on the first and second memoryoperations.

Example 17 includes the system of example 16, wherein the cache storageis a first cache storage, the cache further including a second cachestorage coupled in parallel with the first cache storage.

Example 18 includes the system of example 16, wherein the cache storageis a victim cache storage.

Example 19 includes the system of example 16, wherein the cache furtherincludes a first interface and a second interface, the first interfaceis a 64-bit wide bidirectional scalar interface and the second interfaceis a 512-bit wide vector interface.

Example 20 includes the system of example 16, wherein the replacementpolicy component is operable to adjust the entry reservations in thecache storage based on 1) a validity of the first and second memoryoperations, 2) whether the cache storage stores data for the first andsecond memory operations, and 3) whether the first and second memoryoperations are to allocate data to the cache storage or write data tothe cache storage. FIG. 11A is an example circuit implementation of thevictim cache store queue 216 of FIGS. 2 and/or 3. In FIG. 11A, thevictim cache store queue 216 includes example latches 1102 a, 1102 b,1102 c, 1102 d, 1102 e, example merge circuits 1103 a-c, an examplearithmetic component 1104, an example atomic compare component 1106, anexample read-modify-write merge component 1108, an example selectmultiplexer 1110, and example ECC generator 1112, an example arbitrationmanager 1114, an example pending store address data store 1116, anexample priority multiplexer 1118, and an example write port 1126. Theexample merge circuits 1103 a-d include an example comparator(s) 1120,and example switches 1122. The example of FIG. 11A illustrates a singlepipeline of the victim cache store queue 216. However, the victimstorage element 216 may be arranged to support more than one independentcopy of the pipeline with respect to different banks as indicated by thedashed box 1100. Accordingly, the pipeline of FIG. 11A may be reproducedmultiple times for different banks, as further described below.

Methods and Apparatus for Read-Modify-Write Support in Multi-Banked DataRam Cache for Bank Arbitration

Some monolithic storage devices do not support multiple accesses by aprocessor (e.g., a CPU) during the same clock cycle. For example, arequest to access data in a single main storage can lock up the entiresingle main storage. In such examples, there is a single register filecapable of supporting one full cache line access per clock cycle. Insome such examples, an entire cache line associated with the single mainstorage can be locked to service the request because the single registerfile is allocated to the storage data bank that received such a request.

Examples disclosed herein include multi-banked data RAM cache for bankarbitration. In some disclosed examples, the main cache store queue 212of FIG. 2 has a plurality of banks (e.g., storage banks, storage databanks, memory banks, etc.) and, thus, is multi-banked, or has amulti-bank data or memory structure. In some disclosed examples, themain storage 214 of FIG. 2 has a plurality of banks and, thus, ismulti-banked, or has a multi-bank data or memory structure.Advantageously, the multi-bank structure of the main cache store queue212 and/or the main storage 214 can effectuate support for two or moreaccesses (e.g., CPU accesses) per clock cycle. Advantageously, themulti-bank structure of the main cache store queue 212 and/or the mainstorage 214 allows the two or more accesses to be serviced and/orfulfilled without performance overhead.

In some disclosed examples, arbitration logic is coupled to the maincache storage queue 212 and/or the main storage 214 in an arrangement toresolve bank access conflicts. For example, the main cache storage queue212 can be divided into 16 independently addressable banks. In suchexamples, the arbitration logic can include 16 sets of arbitrationlogic, where each set of the arbitration logic is in circuit with acorresponding one of the 16 independently addressable banks.Advantageously, the arbitration logic can resolve bank access conflictsof a first bank of the 16 banks independently of a second bank of the 16banks.

FIG. 7B is a schematic illustration of a second example encapsulateddata cache system 710. The second encapsulated data cache system 710 canbe an example circuit implementation of the L1 cache 110 of FIG. 1 orportion(s) thereof, and/or, more generally, the data cache 108 of FIG. 1or portion(s) thereof. The second encapsulated data cache system 710 isencapsulated to provide a unified storage view to an external system(e.g., one or more CPUs, one or more processors, external hardware,etc.). For example, the second encapsulated data cache system 710 can beencapsulated using firmware, software, hardware logic, etc., and/or acombination thereof to encapsulate and/or otherwise abstract allcomplexity related to read after write (RAW) hazards, write after write(WAW) hazards, data forwarding, etc. Advantageously, the unifiedarchitecture depicted in the example of FIG. 7B can provide separateports to an external system (e.g., the CPU 102) to simplify obtainingaccess to the most recent versions of data of interest.

In the example of FIG. 7B, the second encapsulated data cache system 710includes the main cache store queue 212 of FIG. 2 and the main storage214 of FIG. 2. In FIG. 7B, the main cache store queue 212 includes aplurality of first example independently addressable banks (e.g., databanks, store banks, data store banks, etc.) 712. For example, the firstindependently addressable banks 712 can be bank queues, bank sub-queues,etc. In such examples, the bank queues, the bank sub-queues, etc., caninclude a plurality of storage elements, as depicted below in FIG. 7Dand/or FIG. 7E. The first independently addressable banks 712 are maincache store queue banks (e.g., main cache store queue data banks, maincache bank queues, main cache bank sub-queues, etc.). In FIG. 7B, themain cache store queue 212 includes 16 of the main cache store queuebanks 712. Alternatively, there may be fewer or more than 16 instancesof the main cache store queue banks 712.

In FIG. 7B, the main storage 214 includes a plurality of second exampleindependently addressable banks (e.g., data banks, store banks, datastore banks, etc.) 714. The second independently addressable banks 714are main storage banks (e.g., main storage data banks). In FIG. 7B, themain storage 214 includes 16 of the main storage banks 714.Alternatively, there may be fewer or more than 16 instances of the mainstorage banks 714. For example, the main cache store queue 212 caninclude a plurality of bank queues or bank sub-queues including a firstbank queue or a first bank sub-queue (e.g., MAIN CACHE STORE QUEUE:BANK 1) and the main storage 214 can include a plurality of data banksincluding a first data bank (e.g., MAIN STORAGE: BANK 1).

In some examples, the main cache store queue 212 and the main storage214 each have 256 rows with each row having a line width of 1024 bits,but being divided into 16 banks as illustrated in FIG. 7B, with 64 bitsper row in a given bank. In some examples, the main cache store queue212 and the main storage 214 each have 384 rows with each row having aline width of 1024 bits, but being divided into 16 banks as illustratedin FIG. 7B, with 64 bits per row in a given bank. Of course, the cachesize described in the above examples are only two examples and thedisclosure is not limited to any particular cache line width, number ofbanks, or rows, etc. As depicted in FIG. 7B, each of the first banks 712correspond to one of the second banks 714. For example, a first bank(BANK 1) of the main cache store queue 212 is in circuit with a firstbank (BANK 1) of the main storage 214 and, thus, corresponds with thefirst bank of the main storage 214.

Advantageously, the multi-bank structure of the main cache store queue212, the main storage 214, and/or, more generally, the secondencapsulated data cache system 710, can service read and writeoperations that are sent to the banks in parallel. In some examples,each bank arbitrates its own processes in response to the read and/orwrite operations. By allowing each bank of the second encapsulated datacache system 710 to operate independently, operation of the secondencapsulated data cache system 710 is more efficient since an entirecache line is not locked up when a request is received. Rather, only theportion of the cache line allocated to the bank that received such arequest would be locked.

FIG. 7D depicts an example main cache multi-bank structure 730. In someexamples, the L1 cache 110, the L2 cache 112, and/or the L3 cache 114 ofFIG. 1 can have the main cache multi-bank structure 730. In someexamples, the main cache store queue 212 of FIG. 2 and/or the mainstorage 214 of FIG. 2 can have the main cache multi-bank structure 730.For example, the main cache multi-bank structure 730 can be an exampleimplementation of the main cache store queue 212 and/or the main storage214.

The main cache multi-bank structure 730 is a data or memory structurethat includes 16 example banks (Banks 0-15) 732, with each of the banks732 having a data width of 64 bytes (e.g., bytes 0-7). Each of the banks732 includes 16 example rows (Rows 0-15) 734, with each of the rows 734having a data width of 128 bytes (e.g., 128 bytes=8 bytes/bank*16banks). In FIG. 7D, each of the banks 732 can store 128 bytes (e.g., 128bytes=8 bytes/row*16 rows). In FIG. 7D, the main cache multi-bankstructure 730 can store 2048 bytes (e.g., 2048 bytes=128 bytes/bank*16banks). The main cache multi-bank structure 730 is independentlyaddressable by bank. For example, the first row of the rows 734 has astarting row address of 0 and an ending row address of 127, a second rowof the rows 734 has a starting row address of 128 and an ending rowaddress of 255, etc.

In some examples, a cache line can be 128 bytes of data that fits in awidth of memory (e.g., DRAM) or storage unit (e.g., the main storage214, the victim storage 218, etc.). In the example of FIG. 7D, a cacheline can consume an entire row of the main cache bank structure 730. Forexample, a cache line can use one of the rows 734 of 16 banks, whereeach bank is 8 bytes wide. Advantageously, the main cache bank structure730 can enable 16 different cache lines to access data stored therein.

FIG. 7E depicts an example unified cache multi-bank structure 740. Insome examples, the L1 cache 110, the L2 cache 112, and/or the L3 cache114 of FIG. 1 can have the unified cache bank structure 740. In someexamples, the main cache store queue 212 of FIG. 2, the main storage 214of FIG. 2, the victim cache store queue 216 of FIG. 2, and/or the victimstorage 218 of FIG. 2 can have the unified cache multi-bank structure740. For example, the unified cache multi-bank structure 740 can be anexample implementation of the main cache store queue 212, the mainstorage 214, the victim cache store queue 216, and/or the victim storage218.

The unified cache multi-bank structure 740 is a data or memory structurethat includes 16 example banks (Banks 0-15) 742, with each of the banks742 having a data width of 64 bytes (e.g., bytes 0-7). Each of the banks742 includes 16 example rows (Rows 0-15) 744, with each of the rows 744having a data width of 128 bytes (e.g., 128 bytes=8 bytes/bank*16banks). In FIG. 7E, each of the banks 742 can store 128 bytes (e.g., 128bytes=8 bytes/row*16 rows). In FIG. 7E, the unified cache multi-bankstructure 740 can store 2048 bytes (e.g., 2048 bytes=128 bytes/bank*16banks). The unified cache multi-bank structure 740 is independentlyaddressable by bank. For example, the first row of the rows 744 has astarting row address of 0 and an ending row address of 127, a second rowof the rows 744 has a starting row address of 128 and an ending rowaddress of 255, etc.

FIGS. 9A and 9B (collectively FIG. 9) depict example instructionservicing workflows 900, 910, 920 that can be executed by the main cachecontroller 222, the victim cache controller 224, and/or, more generally,the cache controller 220 of FIG. 2, and/or, more generally, the L1 cache110 of FIGS. 1 and/or 2. For example, the instruction servicingworkflows 900, 910, 920 can be executed to in connection with at leastone of the main cache store queue 212, the main storage 214, the victimcache store queue 216, or the victim storage 218 of FIG. 2. Theinstruction servicing workflows 900, 910, 920 include a first exampleinstruction servicing workflow 900, a second example instructionservicing workflow 910, and a third example instruction servicingworkflow 920.

The first instruction servicing workflow 900 is executed in response toreceiving a first example store instruction 902. The first storeinstruction 902 is a CPU write operation or command to write 64 bytes ataddress (Addr) 0. The address processing components 302 a-c of FIGS.3A-3D can rotate and/or otherwise organize first data (CPU-Write Data)included in the first store instruction 902 to generate first examplerotated or aligned data (Write-Data Aligned) 904.

The address processing components 302 a-c of FIGS. 3A-3D can use amemory address from the store instruction to determine which banks ofthe main cache store queue 212, the main storage 214, the victim cachestore queue 216, and/or the victim storage 218 of FIG. 2 are needed forthe first store instruction 902. For example, the address processingcomponents 302 a-c can determine that Addr 0 of the first storeinstruction 902 is indicative of 8 entire banks (e.g., 8 of the banks722 of FIG. 7C) to be read from and written to. In such examples, theaddress processing components 302 a-c can determine that the number orquantity of banks to read from is 0x00FF and the number or quantity ofbanks to write to is 0x00FF. For example, the address processingcomponents 302 a-c can determine that Banks 0-7 of FIG. 7C need to beaccessed, where each of the banks has a corresponding bit (e.g., a firstbit for Bank 7, a second bit for Bank 6, a third bit for Bank 5, etc.).When a bank is to be read from or written to, the corresponding bitposition has a bit value of 1 and a bit value of 0 otherwise. In suchexamples, the address processing components 302 a-c can generate anaddress for the number of banks read of 0x00FF, which is 11111111 inbinary, based on each of the bits for Banks 0-7 having a 1 value (e.g.,Bank 7 is 1, Bank 6 is 1, etc.) indicative of that respective bankneeded to be accessed for the first store instruction 902.

In some examples, the bank processing logic 303 of FIGS. 3A-3D detectswhether incoming store instructions, such as the first store instruction902, indicate a write of an entire bank, or a write of a partial bank.In the first instruction servicing workflow 900, the bank processinglogic 303 can determine that, since all of the needed banks are to becompletely overwritten, then none of the banks are needed to be firstread from. For example, the bank processing logic 303 can determine thatthe number of banks read is 0x0000, which is 000000000 in binary and isindicative of each of the banks not needed to be read from.Advantageously, the bank processing logic 303 can reduce the number ofbanks to read from and, thus, improves efficiency and/or otherwiseoptimizes operation of the main cache store queue 212, the main storage214, and/or, more generally, the encapsulated data cache system 700 ofFIG. 7 by executing less read operations compared to previousimplementations of cache systems.

The second instruction servicing workflow 910 is executed in response toreceiving a second example store instruction 912. The second storeinstruction 912 is a CPU write operation or command to write 64 bytes atAddr 3. The address processing components 302 a-c can rotate and/orotherwise organize second data (CPU-Write Data) included in the secondstore instruction 912 to generate second example rotated or aligned data(Write-Data Aligned) 914. For example, the address processing components302 a-c can shift the second data to place the second data in thecorrect lane associated with cache memory, such as the L1 cache 110.

The address processing components 302 a-c can determine that Addr 3 ofthe second store instruction 912 is indicative of 8 entire banks (e.g.,8 of the banks 702 of FIG. 7) to be read from and written to. In suchexamples, the address processing components 302 a-c can determine thatthe number or quantity of banks to read from is 0x01FF and the number orquantity of banks to write to is 0x01FF. For example, the addressprocessing components 302 a-c can determine that Banks 0-8 of FIG. 7need to be accessed, where each of the banks has a corresponding bit(e.g., a first bit for Bank 8, a second bit for Bank 7, a third bit forBank 6, etc.). In such examples, the address processing components 302a-c can generate an address for the number of banks read of 0x01FF,which is 111111111 in binary, based on each of the bits for Banks 0-8having a 1 value (e.g., Bank 8 is 1, Bank 7 is 1, etc.) indicative ofthat respective bank needed to be accessed for the second storeinstruction 912.

In some examples, the bank processing logic 303 of FIGS. 3A-3D detectswhether the third store instruction 922 indicates a write of an entirebank, or a write of a partial bank. In the second instruction servicingworkflow 910, the bank processing logic 303 can determine that whenBanks 0 and 8 are to be completely overwritten, then Banks 0 and 8 donot need to be first read from. For example, the bank processing logic303 can determine that the number of banks read is 0x0101, which is100000001 in binary and is indicative of Banks 0 and 8 not needed to beread from. Advantageously, the bank processing logic 303 can reduce thenumber of banks to read from and, thus, improves efficiency and/orotherwise optimizes operation of the main cache store queue 212, themain storage 214, and/or, more generally, the encapsulated data cachesystem 700 of FIG. 7 by executing less read operations compared toprevious implementations of cache systems.

The third instruction servicing workflow 920 is executed in response toreceiving a third example store instruction 922. The third storeinstruction 922 is a CPU write operation or command to write 64 bytes atAddr 113. The address processing components 302 a-c can rotate and/orotherwise organize second data (CPU-Write Data) included in the thirdstore instruction 922 to generate third example rotated or aligned data(Write-Data Aligned) 924. For example, the address processing components302 a-c can shift the third data to place the third data in the correctlane associated with cache memory, such as the L1 cache 110.

The address processing components 302 a-c can determine that Addr 113 ofthe third store instruction 922 is indicative of 8 entire banks (e.g., 8of the banks 722 of FIG. 7) to be read from and written to. In suchexamples, the address processing components 302 a-c can determine thatthe number or quantity of banks to read from is 0xC07F and the number orquantity of banks to write to is 0xC07F. For example, the addressprocessing components 302 a-c can determine that Banks 0-6 and 14-15 ofFIG. 7 need to be accessed, where each of the banks has a correspondingbit (e.g., a first bit for Bank 15, a second bit for Bank 14, a thirdbit for Bank 6, etc.). In such examples, the address processingcomponents 302 a-c can generate an address for the number of banks readof 0xC07F, which is 1100000001111111 in binary, based on each of thebits for Banks 0-6 and 14-15 having a 1 value (e.g., Bank 15 is 1, Bank14 is 1, Bank 6 is 1, etc.) indicative of that respective bank needed tobe accessed for the third store instruction 922.

In some examples, the bank processing logic 303 of FIGS. 3A-3D detectswhether the third store instruction 922 indicates a write of an entirebank, or a write of a partial bank. In the third instruction servicingworkflow 920, the bank processing logic 303 can determine that Banks 6and 14-15 are to be completely overwritten, then Banks 6 and 14-15 donot need to be first read from. For example, the bank processing logic303 can determine that the number of banks read is 0xC080, which is1100000010000000 in binary and is indicative of Banks 6 and 14-15 notneeded to be read from. Advantageously, the bank processing logic 303can reduce the number of banks to read from and, thus, improvesefficiency and/or otherwise optimizes operation of the main cache storequeue 212, the main storage 214, and/or, more generally, theencapsulated data cache system 700 of FIG. 7 by executing less readoperations compared to previous implementations of cache systems.

FIGS. 10A-1 and 10A-2 (collectively FIG. 10A) illustrate a schematicillustration of an example data cache system 1000. The data cache system1000 can be an example implementation of the L1 cache 110 of FIGS. 1, 2,and/or 3, or portion(s) thereof. The data cache system 1000 includes afirst example bank (ENCAPSULATED DATA CACHE SYSTEM BANK[i]) 1002 of theencapsulated data cache system 700 of FIG. 7B. For example, the firstbank 1002 can correspond to MAIN CACHE STORE QUEUE: BANK 1 and MAINSTORAGE: BANK 1 of FIG. 7B. The first bank 1002 includes a first examplemain cache store queue bank 1004 of the main cache store queue 212 ofFIG. 2, which can be an example implementation of MAIN CACHE STOREQUEUE: BANK 1 of FIG. 7B. The first bank 1002 includes a first examplemain storage bank 1006 of the main storage 214 of FIG. 2, which can bean example implementation of MAIN STORAGE: BANK 1 of FIG. 7B.

The data cache system 1000 includes first example address processinglogic 1001 and second example address processing logic 1003. The firstaddress processing logic 1001 and the second address processing logic1003 can be example implementations of the address processing components302 a-c of FIGS. 3A-3D and/or the bank processing logic 303 of FIGS.3A-3D. The first address processing logic 1001 can be an exampleimplementation of at least one of the first address processing component302 a, the second address processing component 302 b, or the thirdaddress processing component 302 c of FIGS. 3A-3D. The second addressprocessing logic 1001 can be an example implementation of at least oneof the first address processing component 302 a, the second addressprocessing component 302 b, or the third address processing component302 c of FIGS. 3A-3D.

The data cache system 1000 includes example arbitration logic 1008,1010, and example multiplexer logic 1012, 1014, 1016. The arbitrationlogic 1008, 1010 includes first example arbitration logic (e.g., a firstarbiter) 1008 and second example arbitration logic (e.g., a secondarbiter) 1010. The first arbitration logic 1008 is a main storageread/write arbiter (MS R/W ARB[i]) and the second arbitration logic 1010is a main cache store queue (STQ WRITE ARB[i]). The example arbitrationlogic 1008, 1010 of the illustrated example of FIG. 10A is implementedby a logic circuit such as, for example, a hardware processor. However,any other type of circuitry may additionally or alternatively be usedsuch as, for example, one or more analog or digital circuit(s), logiccircuits, programmable processor(s), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)), fieldprogrammable logic device(s) (FPLD(s)), digital signal processor(s)(DSP(s)), etc. The example multiplexer logic 1012, 1014, 1016 of theillustrated example of FIG. 10A is implemented by a logic circuit suchas, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.

The multiplexer logic 1012, 1014, 1016 includes a first examplemultiplexer (MUX1[i]) (e.g., a first multiplexer logic circuit) 1012, asecond example multiplexer (MUX2[i] (e.g., a second multiplexer logiccircuit) 1014, and a third example multiplexer (MUX3[i]) (e.g., a thirdmultiplexer logic circuit) 1016. The multiplexers 1012, 1014, 1016 havea select input (SEL[i]), data inputs (1-3), and an output.

The first data inputs (data input 1) of the multiplexers 1012, 1014,1016 are coupled to the first address processing logic 1001 and thesecond address processing logic 1003. The second data inputs (data input2) of the multiplexers 1012, 1014, 1016 are coupled to the first addressprocessing logic 1001 and the second address processing logic 1003. Thethird data inputs (data input 3) of the multiplexers 1012, 1014, 1016are coupled to the first address processing logic 1001 and the secondaddress processing logic 1003.

The select input of the first multiplexer 1012 is coupled to an outputof the second arbitration logic 1010. The select input of the secondmultiplexer 1014 and the select input of the third multiplexer 1016 arecoupled to outputs of the first arbitration logic 1008. The output ofthe first multiplexer 1012 is coupled to an example write port (WRITEPORT[i]) 1024 of the first main cache store bank 1004. The output of thesecond multiplexer 1014 is coupled to an example read port (READPORT[i]) 1026 of the first main cache store bank 1004. The output of thethird multiplexer 1016 is coupled to an example read/write port(READ/WRITE PORT[i]) 1028 of the first main storage bank 1006. The firstarbitration logic 1008 is coupled to the first address processing logic1001, the second address processing logic 1003, the second arbitrationlogic 1010, and outputs of the first main cache store queue bank 1004.

STQ[i] of FIG. 10A is representative of a single bank of a multi-bankimplementation of the main cache store queue 212. For example, the maincache store queue 212 can have STQ[0]-STQ[15] representative of the maincache store queue 212 having 16 banks. In such examples, each ofSTQ[0]-STQ[15] can store 64 bits (i.e., 8 bytes). In some such examples,STQ[0]-STQ[15], and/or, more generally, the main cache store queue 212,can store 24,576 bits (i.e., 3072 bytes). Alternatively, each ofSTQ[0]-STQ[15] may store a different quantity of bits and, thus, themain cache store queue may store a different quantity of bits.

A plurality of the banks including the first bank 1002, can beencapsulated to form and/or otherwise generate an encapsulated datacache system 1034. For example, the encapsulated data cache system 1034can be an example implementation of the encapsulated data cache system700 of FIG. 7B. Advantageously, each corresponding bank of the maincache store queue 212 and the main storage 214 can be encapsulatedtogether to form and/or otherwise generate example encapsulated datacache banks 1036 for simplification when interacting with externalsystem(s). Each of the encapsulated data cache banks 1036 include anexample encapsulated write port (WRITE PORT (STQ[i])) 438, an exampleencapsulated read port (READ PORT (STQ[i])) 1040, and an exampleencapsulated read/write port (READ/WRITE PORT MS [i])) 1042.

The first address processing logic 1001 and/or the second addressprocessing logic 1003 can obtain example store instructions 1018, 1020,1022 from one(s) of the interface(s) of FIG. 1 of the CPU 102 of FIG. 1.The store instructions 1018, 1020, 1022 include example data, such asWDATA, ADDR, BYTEN, SIZE, and R/W. WDATA corresponds to data (e.g., 64bits of data) to be written and/or otherwise stored in at least one ofthe main cache store queue 212 or the main storage 214. ADDR correspondsto a data address associated with at least one of the main cache storequeue 212 or the main storage 214. BYTEN corresponds to byte enabledata. SIZE corresponds to a data size of a data access operation (e.g.,a read operation, a write operation, a modify operation, etc., and/or acombination thereof). R/W corresponds to whether the store instructionis a read operation or a write operation.

The store instructions 1018, 1020, 1022 include a first example storeinstruction (SCALAR_DP (DP0)) 1018, a second example store instruction(DMA) 1020, and a third example store instruction (VECTOR_DP (DP1))1022. The first store instruction 1018 is transmitted from the scalarinterface of FIG. 1 (e.g., the CPU interface 202 of FIG. 2) and, thus,corresponds to a scalar data path (SCALAR_DP (DP1)) of the data cachesystem 1000. The second store instruction 1020 is transmitted from thememory interface of FIG. 1, such as a direct memory access (DMA)interface and, thus, corresponds to a DMA data path (DMA). The thirdstore instruction 1022 is transmitted from the vector interface of FIG.1 (e.g., the CPU interface 202 of FIG. 2) and, thus, corresponds to avector data path (VECTOR_DP (DP1)) of the data cache system 1000.

The first address processing logic 1001 and/or the second addressprocessing logic 1003 generate transaction data (TRANSACTION_DP0[i],TRANSACTION DMA[i], TRANSACTION DP1[i]) that can be used to execute adata access operation associated with at least one of the main cachestore queue 212 or the main storage 214. The first address processinglogic 1001 can extract, and in some examples rotate, the WDATA fromrespective one(s) of the store instructions 1018, 1020, 1022 andtransmit the extracted and/or rotated WDATA to a respective first inputof the multiplexers 1012, 1014, 1016. For example, the first addressprocessing logic 1001 can extract and rotate first WDATA from the firststore instruction 1018 and transmit the first extracted and rotatedWDATA to the first input of the first multiplexer 1012, the first inputof the second multiplexer 1014, and the first input of the thirdmultiplexer 1016.

The second address processing logic 1003 can determine an address(MS/STQ_ADDR[i]) for one or more of the 16 banks of at least one of thestore queue 212 or the main storage 214. The address can be based on theADDR data included in the store instructions 1018, 1020, 1022. Thesecond address processing logic 1003 can determine a byte enable valueper bank (BYTEN/BANK[i]) based on the BYTEN data included in the storeinstructions 1018, 1020, 1022. The second address processing logic 1003can determine a write bank request (WR_BANK_REQ[i]) and/or a read bankrequest (RD_BANK_REQ[i]) based on the R/W data included in the storeinstructions 1018, 1020, 1022.

The first address processing logic 1001 and/or the second addressprocessing logic 1003 can determine transaction data for respective onesof the store instructions 1018, 1020, 1022. The transaction data caninclude the rotated WDATA data, MS/STQ_ADDR[i], and BYTEN/BANK[i]. Forexample, the first address processing logic 1001 and/or the secondaddress processing logic 1003 can generate first transaction data(TRANSACTION_DP0[i]) based on the first store instruction 1018, secondtransaction data (TRANSACTION_DMA[i]) based on the second storeinstruction 1020, and third transaction data (TRANSACTION_DP1[i]) basedon the third store instruction 1022. In such examples, the first addressprocessing logic 1001 and/or the second address processing logic 1003can transmit the first transaction data to the first inputs of themultiplexers 1012, 1014, 1016, the second transaction data to the secondinputs of the multiplexers 1012, 1014, 1016, and the third transactiondata to the third inputs of the multiplexers 1012, 1014, 1016.

In example operating conditions, the first address processing logic 1001and the second address processing logic 1003 obtain the storeinstructions 1018, 1020, 1022. The first address processing logic 1001and the second address processing logic 1003 generate the first throughthird transaction data based on respective ones of the storeinstructions 1018, 1020, 1022. The first address processing logic 1001and the second address processing logic 1003 transmit the first throughthird transaction data to the multiplexers 1012, 1014, 1016. The secondaddress processing logic 1003 transmit either a read bank request or awrite bank request corresponding to each of the store instructions 1018,1020, 1022.

In example operating conditions, the first arbitration logic 1008determines whether one(s) of the store instructions 1018, 1020, 1022 arerequesting to read one or more banks of the main cache store queue 212or write to one or more banks of the main storage 214. In exampleoperating conditions, the first arbitration logic 1008 prioritizes readoperations over write operations. In example operating conditions, thebank(s) of the store queue 212 can generate an example store queue fullsignal (FULL_SIG[i]) 1030 in response to the store queue 212 being full.In example operating conditions, the bank(s) of the store queue 212 cangenerate an example complete data write signal (COMLETE_DATA_WR_SIG[i])1032.

For example, the first store instruction 1018 can correspond to a writeoperation for Banks 0-4, the second store instruction 1020 cancorrespond to a read operation of Banks 5-9, and the third storeinstruction 1022 can correspond to a read operation of Banks 10-14. Thesecond arbitration logic 1010 can assign DP0 to transmit the firsttransaction data to the write port 1024 of Banks 0-4 (e.g., WRITEPORT[0], WRITE PORT[1], WRITE PORT[2], etc.) because no other data pathsare requesting a write operation to be serviced. The second arbitrationlogic 1010 can assign DP0 by generating a signal (SEL[i]) to instructthe first multiplexer 1012 to select the first transaction data. Thefirst arbitration logic 1008 can assign DMA to transmit the secondtransaction data to the read port 1026 of Banks 5-9 (e.g., READ PORT[4],READ PORT[5], READ PORT[6], etc.) because no other data paths arerequesting a read operation to be serviced in connection with Banks 5-9.The first arbitration logic 1008 can assign DMA by generating a signal(SEL[i]) to instruct the second multiplexer 1014 to select the secondtransaction data. The first arbitration logic 1008 can assign DP1 totransmit the third transaction data to the read port 1026 of Banks 10-14(e.g., READ PORT[9], READ PORT[10], READ PORT[11], etc.) because noother data paths are requesting a read operation to be serviced inconnection with Banks 10-14. The first arbitration logic 1008 can assignDP1 by generating a signal (SEL[i]) to instruct the third multiplexer1016 to select the third transaction data. In such examples, Bank 15 isnot assigned to any of the data paths.

In example operating conditions, if the first store instruction 1018corresponds to a write operation for Banks 0-4 that is split, the firstarbitration logic 1008 can delay and/or otherwise stall the writeoperation. For example, if a first portion of the write operation isassociated with writing to the main cache store queue 212 and a secondportion of the write operation is associated with reading from the mainstorage 214, the first arbitration logic 1008 can instruct the secondarbitration logic 1010 to not service and/or otherwise not assign thefirst transaction data to the write port 1024.

In example operating conditions, if the first store instruction 1018corresponds to a write operation for Banks 0-4 that is split, the maincache store queue 212 can instruct the first arbitration logic 408 toservice the write operation when the complete data has bene assembledfor writing. For example, if a first portion of the write operation isassociated with writing to the main cache store queue 212 and a secondportion of the write operation is associated with reading from at leastone of the main cache store queue 212 or the main storage 214, the firstarbitration logic 1008 can wait to assign the first transaction data tothe read/write port 1028. In such examples, in response to locating dataassociated with the second portion in the main cache store queue 212,the main cache store queue 212 can deliver the located data to the mainstorage 214. In response to delivering the data to the main storage 214,the main cache store queue 212 can generate a signal (e.g., assert alogic high signal) for COMPLETE_DATA_WR_SIG[i] instructing the firstarbitration logic 1010 to service the write operation because thecomplete set of data required for the write operation has been readand/or otherwise assembled for servicing.

FIGS. 10B-1 and 10B-2 (collectively FIG. 10B) illustrate a schematicillustration of an example data cache system 1000 b. The data cachesystem 1000 b can be an example implementation of the L1 cache 110 ofFIGS. 1, 2, and/or 3, or portion(s) thereof. The data cache system 1000b includes a first example bank (ENCAPSULATED DATA CACHE SYSTEM BANK[i])1002 b of the encapsulated data cache system 700 of FIG. 7A. Forexample, the first bank 1002 b can correspond to VICTIM CACHE STOREQUEUE: BANK 1 and VICTIM STORAGE: BANK 1 of FIG. 7A. The first bank 1002b includes a first example victim cache store queue bank 1004 b of thevictim cache store queue 216 of FIG. 2, which can be an exampleimplementation of VICTIM CACHE STORE QUEUE: BANK 1 of FIG. 7A. The firstbank 1002 b includes a first example victim storage bank 1006 b of thevictim storage 218 of FIG. 2, which can be an example implementation ofVICTIM STORAGE: BANK 1 of FIG. 7A.

The data cache system 1000 b includes first example address processinglogic 1001 b, second example address processing logic 1003 b, examplearbitration logic 1008 b, 1010 b, and example multiplexer logic 1012 b,1014 b, 1016 b. The arbitration logic 1008 b, 1010 b includes firstexample arbitration logic (e.g., a first arbiter) 1008 b and secondexample arbitration logic (e.g., a second arbiter) 1010 b. The firstarbitration logic 1008 b is a victim storage read/write arbiter (VS R/WARB[i]) and the second arbitration logic 1010 b is a victim cache storequeue (STQ_V WRITE ARB[i]). The example arbitration logic 1008 b, 1010 bof the illustrated example of FIG. 10B is implemented by a logic circuitsuch as, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.The example multiplexer logic 1012 b, 1014 b, 1016 b of the illustratedexample of FIG. 10B is implemented by a logic circuit such as, forexample, a hardware processor. However, any other type of circuitry mayadditionally or alternatively be used such as, for example, one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

The multiplexer logic 1012 b, 1014 b, 1016 b includes a first examplemultiplexer (MUX1[i]) (e.g., a first multiplexer logic circuit) 1012 b,a second example multiplexer (MUX2[i] (e.g., a second multiplexer logiccircuit) 1014 b, and a third example multiplexer (MUX3[i]) (e.g., athird multiplexer logic circuit) 1016 b. The multiplexers 1012 b, 1014b, 1016 b have a select input (SEL[i]), data inputs (1-3), and anoutput.

The first data inputs (data input 1) of the multiplexers 1012 b, 1014 b,1016 b are coupled to the address processing logic 1001 b, 1003 b. Thesecond data inputs (data input 2) of the multiplexers 1012 b, 1014 b,1016 b are coupled to the address processing logic 1001 b, 1003 b. Thethird data inputs (data input 3) of the multiplexers 1012 b, 1014 b,1016 b are coupled to the address processing logic 1001 b, 1003 b.

The select input of the first multiplexer 1012 b is coupled to an outputof the second arbitration logic 1010 b. The select input of the secondmultiplexer 1014 b and the select input of the third multiplexer 1016 bare coupled to outputs of the first arbitration logic 1008 b. The outputof the first multiplexer 1012 b is coupled to an example write port(WRITE PORT[i]) 1024 b of the first victim cache store bank 1004 b. Theoutput of the second multiplexer 1014 b is coupled to an example readport (READ PORT[i]) 1026 b of the first victim cache store bank 1004 b.The output of the third multiplexer 1016 b is coupled to an exampleread/write port (READ/WRITE PORT[i]) 1028 b of the first victim storagebank 1006 b. The first arbitration logic 1008 b is coupled to theaddress processing logic 1001 b, 1003 b, the second arbitration logic1010 b, and outputs of the first victim cache store queue bank 1004 b.

STQ_V[i] of FIG. 10B is representative of a single bank of a multi-bankimplementation of the victim cache store queue 216. For example, thevictim cache store queue 216 can have STQ_V[0]-STQ_V[15] representativeof the victim cache store queue 216 having 16 banks. In such examples,each of STQ_V[0]-STQ_V[15] can store 64 bits (i.e., 8 bytes). In somesuch examples, STQ_V[0]-STQ_V[15], and/or, more generally, the victimcache store queue 216, can store 24,576 bits (i.e., 3072 bytes).Alternatively, each of STQ_V[0]-STQ_V[15] may store a different quantityof bits and, thus, the victim cache store queue 216 may store adifferent quantity of bits.

A plurality of the banks including the first bank 1002 b, can beencapsulated to form and/or otherwise generate an encapsulated datacache system 1034 b. For example, the encapsulated data cache system1034 b can be an example implementation of the encapsulated data cachesystem 700 of FIG. 7A. Advantageously, each corresponding bank of thevictim cache store queue 216 and the victim storage 218 can beencapsulated together to form and/or otherwise generate exampleencapsulated data cache banks 1036 b for simplification when interactingwith external system(s). Each of the encapsulated data cache banks 1036b include an example encapsulated write port (WRITE PORT (STQ_V[i]))1038 b, an example encapsulated read port (READ PORT (STQ_V[i])) 1040 b,and an example encapsulated read/write port (READ/WRITE PORT MS[i]))1042 b.

The address processing logic 1001 b, 1003 b can obtain example storeinstructions 1018 b, 1020 b, 1022 b from one(s) of the interface(s) ofFIG. 1 of the CPU 102 of FIG. 1. The store instructions 1018 b, 1020 b,1022 b include example data, such as WDATA, ADDR, BYTEN, SIZE, AND R/W.WDATA corresponds to data (e.g., 64 bits of data) to be written and/orotherwise stored in at least one of the victim cache store queue 216 orthe victim storage 218. ADDR corresponds to a data address associatedwith at least one of the victim cache store queue 216 or the victimstorage 218. BYTEN corresponds to byte enable data. SIZE corresponds toa data size of a data access operation (e.g., a read operation, a writeoperation, a modify operation, etc., and/or a combination thereof). R/Wcorresponds to whether the store instruction is a read operation or awrite operation.

The store instructions 1018 b, 1020 b, 1022 b include a first examplestore instruction (SCALAR_DP (DP0)) 1018 b, a second example storeinstruction (DMA) 1020 b, and a third example store instruction(VECTOR_DP (DP1)) 1022 b. The first store instruction 1018 b istransmitted from the scalar interface of FIG. 1 (e.g., the CPU interface202 of FIG. 2) and, thus, corresponds to a scalar data path (SCALAR_DP(DP1)) of the data cache system 1000 b. The second store instruction1020 b is transmitted from the memory interface of FIG. 1, such as adirect memory access (DMA) interface and, thus, corresponds to a DMAdata path (DMA). The third store instruction 1022 b is transmitted fromthe vector interface of FIG. 1 (e.g., the CPU interface 202 of FIG. 2)and, thus, corresponds to a vector data path (VECTOR_DP (DP1)) of thedata cache system 1000 b.

The address processing logic 1001 b, 1003 b can generate transactiondata (TRANSACTION_DP0[i], TRANSACTION DMA[i], TRANSACTION_DP1[i]) thatcan be used to execute a data access operation associated with at leastone of the victim cache store queue 216 or the victim storage 218. Thefirst address processing logic 1001 b can extract, and in some examplesrotate, the WDATA from respective one(s) of the store instructions 1018b, 1020 b, 1022 b and transmit the extracted and/or rotated WDATA to arespective first input of the multiplexers 1012 b, 1014 b, 1016 b. Forexample, the first address processing logic 1001 b can extract androtate first WDATA from the first store instruction 1018 b and transmitthe first extracted and rotated WDATA to the first input of the firstmultiplexer 1012 b, the first input of the second multiplexer 1014 b,and the first input of the third multiplexer 1016 b.

The second address processing logic 1003 b can determine an address(MS/STQ_V_ADDR[i]) for one or more of the 16 banks of at least one ofthe victim cache store queue 216 or the victim storage 218. The addresscan be based on the ADDR data included in the store instructions 1018 b,1020 b, 1022 b. The second address processing logic 1003 b can determinea byte enable value per bank (BYTEN/BANK[i]) based on the BYTEN dataincluded in the store instructions 1018 b, 1020 b, 1022 b. The secondaddress processing logic 1003 b can determine a write bank request(WR_BANK_REQ[i]) and/or a read bank request (RD_BANK_REQ[i]) based onthe R/W data included in the store instructions 1018 b, 1020 b, 1022 b.

The address processing logic 1001 b, 1003 b can determine transactiondata for respective ones of the store instructions 1018 b, 1020 b, 1022b. The transaction data can include the rotated WDATA data,MS/STQ_V_ADDR[i], and BYTEN/BANK[i]. For example, the address processinglogic 1001 b, 1003 b can generate first transaction data(TRANSACTION_DP0[i]) based on the first store instruction 1018 b, secondtransaction data (TRANSACTION_DMA[i]) based on the second storeinstruction 1020 b, and third transaction data (TRANSACTION_DP1[i])based on the third store instruction 1022 b. In such examples, theaddress processing logic 1001 b, 1003 b can transmit the firsttransaction data to the first inputs of the multiplexers 1012 b, 1014 b,1016 b, the second transaction data to the second inputs of themultiplexers 1012 b, 1014 b, 1016 b, and the third transaction data tothe third inputs of the multiplexers 1012 b, 1014 b, 1016 b.

In example operating conditions, the address processing logic 1001 b,1003 b obtain the store instructions 1018 b, 1020 b, 1022 b. The addressprocessing logic 1001 b, 1003 b generate the first through thirdtransaction data based on respective ones of the store instructions 1018b, 1020 b, 1022 b. The address processing logic 1001 b, 1003 b transmitthe first through third transaction data to the multiplexers 1012 b,1014 b, 1016 b. The second address processing logic 1003 b transmiteither a read bank request or a write bank request corresponding to eachof the store instructions 1018 b, 1020 b, 1022 b.

In example operating conditions, the first arbitration logic 1008 bdetermines whether one(s) of the store instructions 1018 b, 1020 b, 1022b are requesting to read one or more banks of the victim cache storequeue 216 or write to one or more banks of the victim storage 218. Inexample operating conditions, the first arbitration logic 1008 bprioritizes read operations over write operations. In example operatingconditions, the bank(s) of the victim cache store queue 216 can generatean example store queue full signal (FULL_SIG[i]) 1030 b in response tothe victim cache store queue 216 being full. In example operatingconditions, the bank(s) of the victim cache store queue 216 can generatean example complete data write signal (COMLETE_DATA_WR_SIG[i]) 1032 b.

For example, the first store instruction 1018 b can correspond to awrite operation for Banks 0-4, the second store instruction 1020 b cancorrespond to a read operation of Banks 5-9, and the third storeinstruction 1022 b can correspond to a read operation of Banks 10-14.The second arbitration logic 1010 b can assign DP0 to transmit the firsttransaction data to the write port 1024 b of Banks 0-4 (e.g., WRITEPORT[0], WRITE PORT[1], WRITE PORT[2], etc.) because no other data pathsare requesting a write operation to be serviced. The second arbitrationlogic 1010 b can assign DP0 by generating a signal (SEL[i]) to instructthe first multiplexer 1012 b to select the first transaction data. Thefirst arbitration logic 1008 b can assign DMA to transmit the secondtransaction data to the read port 1026 b of Banks 5-9 (e.g., READPORT[4], READ PORT[5], READ PORT[6], etc.) because no other data pathsare requesting a read operation to be serviced in connection with Banks5-9. The first arbitration logic 1008 b can assign DMA by generating asignal (SEL[i]) to instruct the second multiplexer 1014 b to select thesecond transaction data. The first arbitration logic 1008 b can assignDP1 to transmit the third transaction data to the read port 1026 b ofBanks 10-14 (e.g., READ PORT[9], READ PORT[10], READ PORT[11], etc.)because no other data paths are requesting a read operation to beserviced in connection with Banks 10-14. The first arbitration logic1008 b can assign DP1 by generating a signal (SEL[i]) to instruct thethird multiplexer 1016 b to select the third transaction data. In suchexamples, Bank 15 is not assigned to any of the data paths.

In example operating conditions, if the first store instruction 1018 bcorresponds to a write operation for Banks 0-4 that is split, the firstarbitration logic 1008 b can delay and/or otherwise stall the writeoperation. For example, if a first portion of the write operation isassociated with writing to the victim cache store queue 216 and a secondportion of the write operation is associated with reading from thevictim storage 218, the first arbitration logic 1008 b can instruct thesecond arbitration logic 1010 b to not service and/or otherwise notassign the first transaction data to the write port 1024 b.

In example operating conditions, if the first store instruction 1018 bcorresponds to a write operation for Banks 0-4 that is split, the victimcache store queue 216 can instruct the first arbitration logic 1008 b toservice the write operation when the complete data has been assembledfor writing. For example, if a first portion of the write operation isassociated with writing to the victim cache store queue 216 and a secondportion of the write operation is associated with reading from at leastone of the victim cache store queue 216 or the victim storage 218, thefirst arbitration logic 1008 b can wait to assign the first transactiondata to the read/write port 1028 b. In such examples, in response tolocating data associated with the second portion in the victim cachestore queue 216, the victim cache store queue 216 can deliver thelocated data to the victim storage 218. In response to delivering thedata to the victim storage 218, the victim cache store queue 216 cangenerate a signal (e.g., assert a logic high signal) forCOMPLETE_DATA_WR_SIG[i] instructing the first arbitration logic 1010 bto service the write operation because the complete set of data requiredfor the write operation has been read and/or otherwise assembled forservicing.

In FIG. 11A, the example laches 1102 a, 1102 b, 1102 c, 1102 d, 1102 e,are electronic devices configured to store information (e.g., bytes,bits, etc.) obtained by the victim cache store queue 216. The examplelatches 1102 a-c pass the write data and information corresponding towhether the write data needs to be combined with the read and correcteddata out of the ECC logic 310 in arithmetic unit 404, the atomic unit406, and/or the RMW merge component 408. In the example of FIG. 11A, thelatch 1102 a is communicatively coupled to the cache controller 220 toobtain read, write, and/or modify instructions. Such read, modify,and/or write instructions may be originate from the CPU 102, andtransmitted to the latch 1102 a via the cache controller 220. Latch 1102a is coupled to latch 1102 b, the tag RAM 210, the arbitration manager1114, and the pending store address data store 1116 to transmit suchread, modify, and/or write instructions to the latch 1102 b, the tag RAM210, the arbitration manager 1114, and the pending store address datastore 1116 in response to a subsequent clock cycle of the cachecontroller 220.

In the example of FIG. 11A, the latch 1102 b is coupled to latch 1102 a,the pending store address data store 1116, latch 1102 c, the prioritymultiplexer 1118, and the comparator(s) 1120 to transmit the obtainedread, modify, and/or write instruction in response to a subsequent clockcycle of the cache controller 220. In this manner, the value obtainedfrom the read, modify, and/or write instruction (e.g., the byte value,the bit value, etc.), propagates through the victim cache store queue216.

The example latch 1102 c is coupled to the latch 1102 b, the prioritymultiplexer 1118, the arithmetic component 1104, the atomic comparecomponent 1106, and the read-modify-write merge component 1108. Thiscoupling enables the latch 1102 c to transmit the value obtained fromthe read, modify, and/or write instruction (e.g., the byte value, thebit value, etc.) to the arithmetic component 1104, the atomic comparecomponent 1106, and/or the read-modify-write merge component 1108 inresponse to a subsequent clock cycle of the cache controller 220. Insome examples disclosed herein, latch 1102 c may transmit the valueobtained from the read, modify, and/or write instruction (e.g., the bytevalue, the bit value, etc.) to one or more of the arithmetic component1104, the atomic compare component 1106, and/or the read-modify-writemerge component 1108. For example, in the event the cache controller 220transmits an instruction to write a bit into a currently stored word,the latch 1102 c may transmit the value obtained from the read, modify,and/or write instruction (e.g., the byte value, the bit value, etc.) tothe read-modify-write merge component 1108. In other examples disclosedherein, though the cache controller 220 may transmit an instruction towrite a bit into a currently stored word, the latch 1102 c may transmitthe value obtained from the read, modify, and/or write instruction(e.g., the byte value, the bit value, etc.) to the arithmetic component1104, the atomic compare component 1106, and/or read-modify-write mergecomponent 1108.

The example latch 1102 d is coupled to the first multiplexer 1110, theECC generator 1112, and the latch 1102 e. This coupling enables thelatch 1102 d to transmit the value obtained from first multiplexer 1110to ECC generator 1112 and/or the latch 1102 f in response to asubsequent clock cycle of the cache controller 220.

The example latch 1102 e is coupled to priority multiplexer 1118 and tothe MUX circuit 316 of FIGS. 3 and/or 11A. This coupling enables thelatch 1102 e to transmit the value obtained from the from the prioritymultiplexer 1118 to MUX circuit 316 in response to a subsequent clockcycle of the cache controller 220. For example, on a read operation bythe CPU 102 to an address that hits the victim storage element 218, aprevious write to the same address could still be inflight (e.g., notcompletely written to the victim storage element 218). In such anexample, the latch 1102 e collects the unwritten data byte(s) andprovides them to the MUX 316 which eventually get sent back to the CPU102.

The example merging circuit 1103 a is coupled to the latch 1102 d, themerging circuit 1103 b, the arithmetic component 1104, the atomiccompare component 1106, and the read-modify-write merge component 1108.The example merging circuit 1103 b is coupled to the merging circuit1103 a, the priority multiplexer 1118, and the merging circuit 1103 c.The example merging circuit 1103 c is coupled to the merging circuit1103 b and the latch 1102 b. The example merging circuits 1103 a-cfacilitate the comparison of read operations in different sections ofthe victim cache store queue 216 to potentially reroute write operationsto be merged with write operations corresponding to the same memoryaddress location, as further described below. Although the example ofFIG. 11A includes three merging circuits 1103 a-c, there may beadditional merging circuits to merge write operations from othersections of the victim cache store queue 216 (e.g., a merging circuitcoupling the output of the latch 1102 d to the output of latch 1102 band/or latch 1102 a, etc.). In some examples, the merging circuits 1103a-c is combined into a single circuit that compares the write operationsfrom the different latches 1102 b-d and reroutes based on matchingmemory addresses in any two or more of the different latches 1102 b-d.

In the example illustrated in FIG. 11A, the arithmetic component 1104 iscoupled to the latch 1102 c, the first multiplexer 1110, and to the ECClogic 312 to perform arithmetic operations on (e.g., increment,decrement, etc.) data from the victim storage 218. Additionally, thearithmetic component 1104 performs histogram operations on the datastored in the victim storage 218. The example arithmetic component 1104of the illustrated example of FIG. 11A is implemented by a logic circuitsuch as, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.Operation of the example arithmetic component 1104 is further describedbelow.

In the example illustrated in FIG. 11A, the atomic compare component1106 is coupled to the latch 1102 c, the first multiplexer 1110, and tothe ECC logic 312 to compare data at a memory address to a key and, inthe event the data at the memory address matches the key, replace thedata. The example atomic compare component 1106 the illustrated exampleof FIG. 11A is implemented by a logic circuit such as, for example, ahardware processor. However, any other type of circuitry mayadditionally or alternatively be used such as, for example, one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc. Operation of the exampleatomic compare component 1106 is further described below.

In the example illustrated in FIG. 11A, the read-modify-write mergecomponent 1108 is coupled to the latch 1102 c, the first multiplexer1110, and to the ECC logic 312 to facilitate the read, modify, and/orwrite instruction(s) sent by the cache controller 220. For example, theread-modify-write merge component 1108 is coupled to the ECC logic 312to obtain the currently stored word that is to be affected by the read,modify, and/or write instruction(s). In an example write operation, theread-modify-write merge component 1108 is configured to update thecurrently stored word obtained from the ECC logic 312 with the newbit(s), byte(s), etc., obtained from the latch 1102 c. Additionaldescription of the read-modify-write merge component 1108 is describedbelow. The example read-modify-write merge component 1108 of theillustrated example of FIG. 11A is implemented by a logic circuit suchas, for example, a hardware processor. However, any other type ofcircuitry may additionally or alternatively be used such as, forexample, one or more analog or digital circuit(s), logic circuits,programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)), field programmablelogic device(s) (FPLD(s)), digital signal processor(s) (DSP(s)), etc.

The example first multiplexer 1110 is coupled to the arithmeticcomponent 1104, the atomic compare component 1106, and theread-modify-write merge component 1108 to transmit, based on anindication from the cache controller 220, the output of either thearithmetic component 1104, the atomic compare component 1106, or theread-modify-write merge component 1108 to the latch 1102 d. For example,in the event the cache controller 220 indicates to perform a writefunction (e.g., the cache control transmits a write request to the latch1102 b), an indication is sent by the cache controller 220 to the firstmultiplexer 1110 to select the input connected to the read-modify-writemerge component 1108 to be transmitted to the latch 1102 d. The examplefirst multiplexer 1110 of the illustrated example of FIG. 11A isimplemented by a logic circuit such as, for example, a hardwareprocessor. However, any other type of circuitry may additionally oralternatively be used such as, for example, one or more analog ordigital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

In the example illustrated in FIG. 11A, the ECC generator 1112 iscoupled to the latch 1102 d and to the latch 1102 f to facilitate errordetection and correction in the value (e.g., byte(s), bit(s), etc.)stored in the latch 1102 d. For example, the ECC generator 1112 isconfigured to regenerate the ECC value (e.g., generate error detectioncode) which will be stored with the data (e.g., the merged word outputfrom the read-modify-write merge component 1108. The ECC value is usedby the error detection and correction circuit to determine whether theerror occurred during a read and/or write operation, as furtherdescribed above. The example ECC generator 1112 of the illustratedexample of FIG. 11A is implemented by a logic circuit such as, forexample, a hardware processor. However, any other type of circuitry mayadditionally or alternatively be used such as, for example, one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

In FIG. 11A, the example arbitration manager 1114 is coupled to thelatch 1102 a, the latch 1102 b, the pending store address datastore1116, and the victim storage 218 to facilitate the read, modify, and/orwrite instructions obtained from the cache controller 220. For example,in the event a write instruction is received from the cache controller220, the arbitration manager 1114 is configured to transmit a readinstruction of the corresponding currently stored word to the victimstorage 218. In addition, the arbitration manager 1114 is coupled to thevictim storage 218 to arbitrate between conflicting accesses of thevictim storage 218. When multiple operations attempt to access thevictim storage 218 in the same cycle, the arbitration manager 1114 mayselect which operation(s) are permitted to access the victim storage 218according to a priority scheme. Suitable priority schemes are describedin more detail in below; however, in one example, the arbitrationprioritizes read operations over write operations because write datathat is in the victim cache store queue 216 is available for use bysubsequent operations even before it is written to the victim storage218. Thus, there is minimal performance impact in allowing the writedata to wait in the victim cache store queue 216. However, as the victimcache store queue 216 fills with write data that has not yet beenwritten back, the priority of the write operations may increase untilthey are prioritized over competing read operations.

The example arbitration manager 1114 of the illustrated example of FIG.11A is implemented by a logic circuit such as, for example, a hardwareprocessor. However, any other type of circuitry may additionally oralternatively be used such as, for example, one or more analog ordigital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field programmable logic device(s) (FPLD(s)),digital signal processor(s) (DSP(s)), etc.

In the example of FIG. 11A, the pending store address data store 1116 isconfigured to store the address of the read, modify, and/or writeinstruction obtained from the cache controller 220. In this manner, thepending store address datastore 1116 maintains a log of the addressesassociated with each value stored in any of the latches 1102 a, 1102 b,1102 c, 1102 d, 1102 e, 1102 f, 1102 g, and/or 1102 h. The examplepending store address datastore 1116 of the illustrated example of FIG.11A may be implemented by any device for storing data such as, forexample, flash memory, magnetic media, optical media, etc. Furthermore,the data stored in the pending store address datastore 1116 may be inany data format such as, for example, binary data, comma delimited data,tab delimited data, structured query language (SQL) structures, etc.

The example priority multiplexer 1118 is coupled to the latch 1102 b,the latch 1102 c, the latch 1102 d, and the latch 1102 f to facilitateread operations in the event either of the of the latch 1102 b, thelatch 1102 c, the latch 1102 d, or the latch 1102 f are storing a valuecorresponding to a write instruction. For example, the cache controllermay initiate the following four write instructions regarding a four bitword having addresses A3, A2, A1, and A0: write address A0 with the byte0x11, write address A1 with the byte 0x22, write address A3 with thebyte 0x23, and write address A0 with the byte 0x44. In such an example,in the event the cache controller 220 initiates a read instruction toread the entire four bit word, the priority multiplexer 1118 isconfigured to obtain the byte value 0x11 stored in the latch 1102 f, thebyte value 0x22 stored in the latch 1102 d, the byte value 0x23 storedin the latch 1102 c, and the byte value 0x22 stored in the latch 1102 b.Additionally, the pending store address data store 1116 transmits aninstruction to the priority multiplexer 1118 indicating which addressvalue in is associated with the byte value stored in the latch 1102 b,the latch 1102 c, the latch 1102 d, and the latch 1102 f. In such anexample, since the byte value stored in the latch 1102 b is associatedwith the address A0 and the byte value stored in the latch 1102 f isalso associated with the address A0, the priority multiplexer 1118 isconfigured to transmit a packet to the latch 1102 e indicating thataddress A0 is 0x44 (e.g., the most recent write instruction associatedwith the address A0), address A1 is 0x22, and address A3 is 0x23.

In this manner, the MUX circuit 316 is configured to update the value ofthe currently stored word with the byte values obtained from thepriority multiplexer 1118. Such an operation ensures that a readinstruction transmitted by the victim cache store queue 216 probablyindicates the correct word, even though the write instructions may nothave fully propagated through the victim cache store queue 216.

An example read path (e.g., the read input to the tag RAM 210) may runin parallel with the victim cache store queue 216. Because a readoperation (e.g., a read instruction) may refer to data in a writeoperation (e.g., a write instruction) that may not have completed yet,the victim cache store queue 216 may include write forwardingfunctionality that allows the read path to obtain data from the victimcache store queue 216 that has not yet been written back to the victimstorage 218. In an example, the victim cache store queue 216 includespending store address data store 1116 that records the addresses of theoperations at each stage of the victim cache store queue 216, a prioritymultiplexer 1118 to select data from one of the stages (e.g., latches)of the victim cache store queue 216 for forwarding, and a MUX circuit316 that selects between the output of the victim storage 218 (by way ofthe error detection and correction circuit 312) and the forwarded victimcache store queue 216 data from the data priority multiplexer 1118.

The example write port 1126 is coupled to the write path and the latch1102 a. The write port 1126 may be implemented by an interface thatinterfaces with the victim cache controller 224 (e.g., the cachecontroller 220) to obtain a write instruction. For example, the writeport 1126 is utilized to receive addresses and values from the cachecontroller 220 to write.

An example flow of a read operation through the victim cache store queue216 will now be described. In a first cycle, the L1 data cache 110retrieves a record from the tag RAM 210 that is associated with anaddress of the read operation to determine whether the data is stored inthe victim storage 218. In a direct mapped example, the L1 data cache110 need not wait for the tag RAM 210 comparison before requesting datafrom the victim storage 218, and thus, the tag RAM 210 comparisonbetween the address of the read operation and the record of cachedaddresses may extend into a second or third clock cycle.

In the second cycle, the L1 data cache 110 may request the data and ECCsyndrome bits from the victim storage 218 if the arbitration manager1114 permits. In this cycle, the L1 data cache 110 may also determinewhether newer data is available in the victim cache store queue 216 bycomparing the read address to the pending store address data store 1116.If so, the priority multiplexer 1118 is set to forward the appropriatedata from the victim cache store queue 216.

Data and ECC may be provided by the victim storage 218 in the thirdcycle. However, this data may or may not correspond to the memoryaddress specified by the read operation because the L1 data cache 110may allocate multiple extended memory addresses to the same entry in thecache's victim storage 218. Accordingly, in the third cycle, the L1 datacache 110 determines whether the provided data and ECC from the victimstorage 218 corresponds to the memory address in the read operation(e.g., a cache hit) based on the comparison of the tag RAM 210 record.In the event of a cache hit, the data and ECC bits are received by theerror detection and correction circuit 312, which corrects any errors inthe data in a fourth cycle.

As explained above, newer data that has not yet been written to thevictim storage 218 may be present in the victim cache store queue 216,and may be forwarded from the victim cache store queue 216 by thepriority multiplexer 1118. If so, the MUX circuit 316 selects theforwarded data over the corrected data from the victim storage 218.

Either the corrected data from the victim storage 218 or the forwardeddata from the victim cache store queue 216 is provided to the L1 datacache 110 in a fifth cycle. In this way, the controller 220 may providedata with full ECC checking and correction in the event of a cache hitin about 5 cycles.

In the event that the data and ECC bits are not present in the victimstorage 218 (e.g., a cache miss), the victim cache store queue 216 maystall until the data can be retrieved from either the extended memory106 and/or the victim storage 218, at which point the data may bewritten to the victim storage and the tag RAM 210 may be updated.

FIGS. 11B-1 and 11B-2 (collectively FIG. 11B) illustrate a schematicillustration of an example unified cache store queue 1124. In theexample illustrated in FIG. 11B, the unified cache store queue 1124 mayimplement the example main cache store queue 212 and/or the victim cachestore queue 216. In this manner, the topology illustrates example maincache read and write inputs 1128 and example victim cache read and writeinputs 1130. For example, the main cache read and write inputs 1128 mayimplement the example read and write inputs of the main cache storequeue 212 of FIGS. 2 and/or 4, and the victim cache read and writeinputs 1130 may implement the example read and write inputs of thevictim cache store queue 216 of FIGS. 2 and/or 11A. In the example ofFIG. 11B, the main cache read and write inputs 1128 are pipelinedseparately from the victim cache read and write inputs 1130.Accordingly, in operation, the main cache read and write inputs 1128and/or the victim cache read and write inputs 1130 are configured toobtain read and/or write instructions from the CPU 102. In some examplesdisclosed herein, the main cache read and write inputs 1128 and thevictim cache read and write inputs 1130 may be referred to as inputs ofthe unified cache store queue 1124.

The unified cache store queue 1124 includes an example first pipestage(E2) 1132, an example second pipestage (E3) 1134, and an example fourthpipestage (E4) 1136. In this manner, the unified cache store queue 1124is coupled to the first pipestage (E2) 1132 via example data pipestages1138 and 1140, and the main storage 214 and the victim storage 218 ofFIG. 2.

In operation, the CPU 102 transmits a read and/or a write instruction,which enters the unified cache store queue 1124 via the first pipestage(E2) 1132. In other examples disclosed herein, the unified cache storequeue 1124 may obtain a read and/or write instruction from the CPU 102via the cache controller 220. At this point, the example L1 cache 110compares the address of incoming read and/or write instruction with themain cache tag ram 208 and the victim cache tag ram 210. Additionally,the determination of whether the read and/or write instruction isindented for the main storage 214 or the victim storage 218 is not yetknown to the unified cache storage queue 1124.

In response to a subsequent clock cycle of the CPU 102, or the cachecontroller 202, the read and/or write instruction is transmitted to thethird pipestage (E3) 1134. At this point, the L1 cache 110 determines,or has determined, if the read and/or write instruction is intended forthe main storage 214 or the victim storage 218. Such a determination istransmitted to the unified cache store queue 1124 as a hit and/or misssignal.

In FIG. 11B, the physical address of the main storage 214 is a functionof the CPU 102 address. The CPU 102 address determines which set of thedirect mapped main storage 214 that maps to the CPU 102 address. In FIG.11B, the size of the main storage 214 is 32 kilobytes (KB), and thecache line size is 128 byes, totaling 256 sets. Thus, the physicaladdress of the CPU 102 may range from Address A0 to Address A255.

In FIG. 11B, the physical address of victim storage 216 is based on thefollowing logic. First, the CPU 102 address is compared with all 16entries of the victim storage 216. In the event the CPU 102 addresscorresponds to a hit in the victim storage 216, then the location ofentry where the CPU 102 transaction hits is the physical address.

However, if the CPU 102 address does not correspond to a hit (e.g.,corresponds to a miss), then the replacement policy chooses a locationinside the victim storage 216. Since there are 16 physical address ofthe victim storage 216, the CPU 102 address may range from A0 to A15.

In the example of FIG. 11B, the information corresponding to whether theCPU 102 address is a hit or a miss is sent to the unified cache storequeue 1124. Based on this information, the read and/or write instructionobtained by the CPU 102 enters either the main cache store queue 212 ofthe unified cache store queue 1124 or the victim cache store queue 216of the unified cache store queue 1124.

Example methods, apparatus, systems, and articles of manufacture forread-modify-write support in multi-banked data ram cache for bankarbitration are disclosed herein. Further examples and combinationsthereof include the following:

Example 1 includes a data cache system comprising a store queueincluding a plurality of bank queues, the plurality of the bank queuesincluding a first bank queue, the first bank queue having a write portand a read port, the write port configured to receive a write operation,the read port configured to receive a read operation, storage coupled tothe store queue, the storage including a plurality of data banks, theplurality of the data banks including a first data bank, the first databank having a first port configured to receive the write operation orthe read operation, a first multiplexer having a first select input anda first output, the first output coupled to the write port, a secondmultiplexer having a second select input and a second output, the secondoutput coupled to the read port, a third multiplexer having a thirdselect input and a third output, the third output coupled to the firstport, and bank arbitration logic including first arbiters and secondarbiters, the first arbiters including a first arbiter and the secondarbiters including a second arbiter, the first arbiter coupled to thesecond arbiter, the second select input, and the third select input, thesecond arbiter coupled to the first select input.

Example 2 includes the data cache system of example 1, further includingfirst address control logic coupled to a first input of the firstarbiter, a first input of the second arbiter, a first input of the firstmultiplexer, a first input of the second multiplexer, and a first inputof the third multiplexer, second address control logic coupled to asecond input of the first arbiter, a second input of the second arbiter,a second input of the first multiplexer, a second input of the secondmultiplexer, and a second input of the third multiplexer, and thirdaddress control logic coupled to a third input of the first arbiter, athird input of the second arbiter, a third input of the firstmultiplexer, a third input of the second multiplexer, and a third inputof the third multiplexer.

Example 3 includes the data cache system of example 2, further includinga first interface coupled to an input of the first address controllogic, the first interface coupled to a scalar data path, a secondinterface coupled to an input of the second address control logic, thesecond coupled to a direct memory access data path, and a thirdinterface coupled to an input of the third address control logic, thethird interface coupled to a vector data path.

Example 4 includes the data cache system of example 3, further includingfirst write data rotate logic coupled to the first interface and thefirst input of the first multiplexer, the first input of the secondmultiplexer, and the first input of the third multiplexer, second writedata rotate logic coupled to the second interface and the second inputof the first multiplexer, the second input of the second multiplexer,and the second input of the third multiplexer, and third write datarotate logic coupled to the third interface and the third input of thefirst multiplexer, the third input of the second multiplexer, and thethird input of the third multiplexer.

Example 5 includes the data cache system of example 1, wherein a firstoutput of the first bank queue is coupled to a first input of the firstarbiter and a first input of the second arbiter.

Example 6 includes the data cache system of example 1, wherein theplurality of the bank queues is a first quantity and the plurality ofthe data banks is a second quantity, where the first quantity is thesame as the second quantity.

Example 7 includes the data cache system of example 1, wherein thestorage is a dynamic random access memory, and the plurality of the databanks has a quantity of 16 data banks, each of the 16 data banks havinga data width of 64 bytes.

Example 8 includes an encapsulated data cache system comprisingencapsulated memory that includes a plurality of bank queues having arespective read port and a respective write port, and a plurality ofdata banks having a respective first port, the first port configured toreceive a read operation or a write operation, a read port coupled tothe encapsulated memory, the read port representative of the respectiveread port of the bank queues, the read port configured to read firstdata stored at one or more of the bank queues, a write port coupled tothe encapsulated memory, the write port representative of the respectivewrite port of the bank queues, the write port configured to write seconddata to one or more of the data banks, and a second port coupled to theencapsulated memory, the second port representative of the respectivefirst port of the data banks, the second port configured to read thirddata from one or more of the data banks or write fourth data to one ormore of the data banks.

Example 9 includes the encapsulated data cache system of example 8,further including a multiplexer having a select input and a firstoutput, the first output coupled to the read port, and arbiter logiccoupled to the select input, the arbiter logic to assign a firstinterface of a plurality of interfaces to a first bank queue of the bankqueues and a first data bank of the data banks, the first interface totransmit transaction data from the first interface to the read port toinvoke the read port to read at least one of the first data from thefirst bank queue or the third data from the first data bank.

Example 10 includes the encapsulated data cache system of example 9,further including address processing logic coupled to the firstinterface and the arbiter logic, the address processing logic toidentify the first bank queue based on address data included in thetransaction data.

Example 11 includes the encapsulated data cache system of example 9,wherein the multiplexer is a first multiplexer, the select input is afirst select input, the transaction data is first transaction data, andfurther including a second multiplexer having a second select input anda second output, the second output coupled to the second port, and thearbiter logic coupled to the second select input, the arbiter logic toassign a second interface of the plurality of the interfaces to a secondbank queue of the bank queues and a second data bank of the data banks,the second interface to transmit second transaction data from the secondinterface to the second port to invoke the second port to read at leastone of the first data from the second bank queue or the third data fromthe second data bank.

Example 12 includes the encapsulated data cache system of example 11,wherein the second port is to read data from the second bank queue andthe second data bank during a first time and the read port is to read atleast one of the first data from the first bank queue or the third datafrom the first data bank during the first time.

Example 13 includes the encapsulated data cache system of example 9,wherein the multiplexer is a first multiplexer, the select input is afirst select input, the transaction data is first transaction data, thearbiter logic is first arbiter logic, and further including a secondmultiplexer having a second select input and a second output, the secondoutput coupled to the write port, and second arbiter logic coupled tothe second select input, the second arbiter logic to not assign a secondinterface of the plurality of the interfaces to a second bank queue ofthe bank queues in response to the first arbiter logic not assigning thesecond interface to a second data bank of the data banks.

Example 14 includes the encapsulated data cache system of example 8,further including first arbiter logic coupled to the write port, andsecond arbiter logic coupled to the read port, the first port, and thefirst arbiter logic, the second arbiter logic to instruct the firstarbiter logic to cause the write port to write the second data to theone or more of the bank queues in response to the bank queues havingcapacity to store the second data.

Example 15 includes the encapsulated data cache system of example 8,further including first arbiter logic coupled to the write port, andsecond arbiter logic coupled to the read port, the first port, and thefirst arbiter logic, the second arbiter logic to instruct the firstarbiter logic to cause the write port to write the second data to theone or more of the bank queues in response to at least one of the firstdata retrieved from the one or more bank queues or the third dataretrieved from the one or more data banks.

Example 16 includes a method comprising generating first transactiondata based on first instructions from a processor and second transactiondata based on second instructions from the processor, the firsttransaction data indicative of a first quantity of data banks to accessfor first data, the second transaction data indicative of a secondquantity of data banks to access for second data, locating the firstdata for a first data access operation in a first data bank of at leastone of a store queue or storage, locating second data for a second dataaccess operation in a second data bank of at least one of the storequeue or the storage, and in response to the first data bank beingdifferent from the second data bank, assigning the first transactiondata to be transmitted to the first data bank and the second transactiondata to be transmitted to the second data bank.

Example 17 includes the method of example 16, further including inresponse to the first data bank being the same as the second data bank,determining whether the first data access operation or the second dataaccess operation is a read data operation or a write data operation, andin response to the first data access operation being the read dataoperation and the second data access operation being a write dataoperation, assigning the first transaction data to be transmitted to thefirst data bank and not assigning the second transaction data to betransmitted.

Example 18 includes the method of example 16, wherein the first dataaccess operation includes reading a first portion of the first data fromone or more of the first data banks and writing a second portion of thefirst data to one or more of the second data banks, the first data bankincluded in the one or more of the first data banks or the one or moreof the second data banks, and further including in response to locatingthe first portion in the first data banks of the store queuetransmitting the first portion from the store queue to the storage,transmitting a control signal from the store queue to arbiter logic, thearbiter logic coupled to the storage, and in response to the arbiterlogic obtaining the control signal, writing the first portion and thesecond portion to the storage.

Example 19 includes the method of example 16, wherein the first databank is included in the store queue, and further including, in responseto the store queue being full, instructing arbiter logic coupled to thestore queue to prevent assigning the first transaction to be transmittedto the first data bank.

Example 20 includes the method of example 16, further includingdetermining a data access operation data size based on the firstinstructions, determining a data storage address based on the firstinstructions, mapping the data access operation data size and the datastorage address to the first quantity of data banks to be accessed, thefirst quantity of data banks including a first data bank and a seconddata bank, and determining that the data access operation includesreading a first portion of the first data from the first data bank andwriting a second portion of the first data to the second data bank.

Methods and Apparatus to Facilitate Read-Modify-Write Support in aVictim Cache

In examples disclosed herein, the victim storage 218 includes multiplememory banks, each bank being 64 bits wide. The victim storage 218 isparallel coupled with the main storage 214. Additionally, the banks inthe victim storage 218 include two 32-bit parity blocks. In examplesdisclosed herein, 7 bits of ECC syndrome is stored for each of the32-bit party blocks. Thus, the overall bank width is 118 bits. In otherexamples disclosed herein, any suitable bank width may be utilized.

In an example operation, in the event the cache controller 220 transmitsa write instruction to the victim storage 218, and in the event thewrite instruction is not aligned with a parity block on the victimstorage 218, the cache controller 220 indicates to the victim cachestore queue 216 to perform a read-modify-write operation.

In examples disclosed herein, there are two cache systems operating intandem (e.g., the main storage 214 and the victim cache storage 218). Inexamples disclosed herein, the main storage 214 is a direct mapped cacheelement and the victim cache storage 218 is a fully associative cachestorage. Both the direct mapped main storage 214 and the fullyassociative victim cache storage 218 are protected by an errorcorrecting code (ECC). With this, example applications include reading aline from main storage 214, the ECC logic would correct the cache lineand regenerate the ECC syndrome, and then write the line to victim cachestorage 218. Such an application may utilize two additional clock cyclesof the CPU (e.g., one clock cycle for error correction by the ECC logicand another clock cycle for ECC syndrome regeneration). To reduce thislatency, examples disclosed herein include utilizing the same parityblock size between the main storage 214 and the victim cache storage218. Thus, both the main storage 214 and the victim cache storage 218calculate and/or otherwise determine parity on a 32-bit boundary. Inthis manner, the L1 cache 110 can move a cache line directly from mainstorage 214 to the victim cache storage 218 with less latency.

In examples disclosed herein, the L1 data cache 110 supports a number ofoperations that read data from the cache and make changes to the databefore rewriting it. For example, the L1 data cache 110 may supportread-modify-write operations. A read-modify-write operation readsexisting data and overwrites at least portion of the data. In ECCembodiments, a read-modify-write operation may be performed when writingless than a full bank width. The read functionality of theread-modify-write is used because the portion of the data in the bankthat will not be overwritten still contributes to the ECC syndrome bits.

A read-modify-write operation may be split into a write operation and aread operation, and the victim cache store queue 216 may be structuredsuch that the read operation in the read path stays synchronized withthe write operation in the victim cache store queue 216. The readoperation and the write operation remain synchronized until theread-modify-write merge component 1108 overwrites at least a portion ofthe read data with the write data to produce merged data. The mergeddata is provided to the ECC generator 1112 that generates new ECCsyndrome bits for the merged data, and then the merged data and ECCsyndrome bits may be provided to the arbitration manager 1114 forstoring in the victim storage 218.

In an example read operation, the L1 data cache 110 compares an addressof the read operation to a record of the tag RAM 210, and the L1 datacache requests the data and ECC syndrome bits from the victim storage218 and/or the victim cache store queue 216. Because theread-modify-write operation will modify the data, in examples that trackMESI (Modified, Exclusive, Shared, and Invalid) states of entries in thevictim storage 218, a cache hit that is not in either the Modified orExclusive state may be considered a cache miss. When the data isobtained in the proper state and any errors are corrected, it isprovided to the read-modify-write merge component 1108. In this samecycle, the read-modify-write merge component 1108 may overwrite at leasta portion of the corrected data with the write data to produce mergeddata. The ECC generator 1112 generates new ECC syndrome bits for themerged data.

In an example write operation, the cache controller 220 of FIGS. 2and/or 3 transmits a write request indicating byte(s) of a word, or anentire word, to be re-written. In such an example, the write requesttransmitted by the cache controller 220 includes an address value of thebyte and the byte value (e.g., a set of data). For example, the victimstorage 218 of FIGS. 2 and/or 3 may include the four-bit word 0x12345678associated with addresses A3, A2, A1, A0. In such an example, address A3corresponds to the byte 0x12, address A2 corresponds to the byte 0x34,address A1 corresponds to the byte 0x56, and address A0 corresponds tothe byte 0x78 of the stored word. In such an example operation, thecache controller 220 may transmit a write request to replace address A3with the byte 0x33, replace address A1 with the byte 0x22, and replaceaddress A0 with the byte 0x11 of the currently stored word 12345678.Further in such an example, the first write request to replace addressA3 of the stored word with the byte 0x33 would result in the stored wordbecoming 0x33345678, the second write request to replace address A1 ofthe stored word with the byte 0x22 would result in the stored wordbecoming 0x33342278, and the third write request to replace address A0of the stored word with the byte 0x11 would result in the stored wordbecoming 0x33342211.

To coordinate such a request, at a first example cycle (e.g., to competethe first write request of replacing address A3 with the byte 0x33),because the ECC generator 1112 operates on word granularity, the cachecontroller 220 initiates a read request of the currently stored byte(e.g., a read request of a second set of data stored in the victimstorage 218) in address A3 of the currently stored word. In thisexample, the byte and address in the first write request (e.g., 0x33 andA3) is stored in the latch 1102 b. In addition, the cache controller 220transmits a read request of the entire currently stored word to thevictim storage 218. Thus, at the end of the first cycle, a read requestof the entire currently stored word is transmitted to the victim storage218 and the byte 0x33 is stored in the first latch 1102 b.

At an example second cycle (e.g., to complete the second write requestof replacing address A1 with the byte 0x22) the byte from the firstwrite request is transmitted to the latch 1102 c, the entire currentlystored word is transmitted from the victim storage 218 to the ECC logic312, and the second write request (e.g., to replace address A1 with thebyte 0x22) is transmitted by the cache controller 220 to be stored inthe latch 1102 b. During the second cycle, the read-modify-write mergecomponent 1108 obtains the byte stored in the latch 1102 c and theentire currently stored word transmitted by the ECC logic 312. In thismanner, the read-modify-write merge component 1108 identifies theaddress of the byte in the currently stored word to be updated. Once theread-modify-write merge component 1108 identifies and/or otherwiseobtains (a) the value (e.g., byte value, bit value, etc.) of the portionof the currently stored word to be updated from the latch 1102 c and the(b) currently stored word from the ECC logic 312, the read-modify-writemerge component 1108 writes (e.g., replaces, merges, etc.) the portionof the currently stored word (e.g., the second set of data) with thevalue of the portion of the currently stored word obtained from thelatch 1102 c (e.g., the first set of data). For example, theread-modify-write merge component 1108 writes the value of the portionof the word to an address value corresponding to the portion of the wordin the word. In some examples disclosed herein, such a merged set ofdata is provided by the read-modify-write merge component 1108 forwriting to the victim storage 218.

Example methods, apparatus, systems, and articles of manufacture tofacilitate read-modify-write support in a victim cache are disclosedherein. Further examples and combinations thereof include the following:

Example 1 includes an apparatus comprising a first storage coupled to acontroller, a second storage coupled to the controller and parallelcoupled to the first storage, and a storage queue coupled to the firststorage, the second storage, and to the controller, the storage queue toobtain a memory operation from the controller indicating an address anda first set of data, obtain a second set of data associated with theaddress from at least one of the first storage and the second storage,merge the first set of data and the second set of data to produce athird set of data, and provide the third set of data for writing to atleast one of the first storage and the second storage.

Example 2 includes the apparatus of example 1, wherein the memoryoperation is a read memory operation indicating to read the second setof data associated with the address from at least one of the firststorage and the second storage.

Example 3 includes the apparatus of example 2, wherein the storage queueis configured to obtain the read memory operation prior to merging thefirst set of data and the second set of data.

Example 4 includes the apparatus of example 1, wherein the store queueincludes an error correcting code generator configured to generate errorcorrecting code syndrome bits.

Example 5 includes the apparatus of example 1, wherein the first storageis a main storage and the second storage is a victim storage, the mainstorage and the victim storage located within a level one cache.

Example 6 includes the apparatus of example 1, wherein the controller isa cache controller configured to be coupled to a central processing unitinterface to obtain the memory operation from a central processing unit.

Example 7 includes a system comprising a central processing unitconfigured to generate a memory operation, a first storage coupled tothe central processing unit, a second storage coupled to the centralprocessing unit and parallel coupled to the first storage, and a storagequeue coupled to the first storage, the second storage, and to thecentral processing unit, the storage queue to obtain the memoryoperation from the central processing unit indicating an address and afirst set of data, obtain a second set of data associated with theaddress from at least one of the first storage and the second storage,merge the first set of data and the second set of data to produce athird set of data, and provide the third set of data for writing to atleast one of the first storage and the second storage.

Example 8 includes the system of example 7, wherein the memory operationis a read memory operation indicating to read the second set of dataassociated with the address from at least one of the first storage andthe second storage.

Example 9 includes the system of example 8, wherein the storage queue isconfigured to obtain the read memory operation prior to merging thefirst set of data and the second set of data.

Example 10 includes the system of example 8, wherein the store queueincludes an error correcting code generator configured to generate errorcorrecting code syndrome bits.

Example 11 includes the system of example 10, wherein the errorcorrecting code generator generates the error correcting code syndromebits in response to merging the first set of data and the second set ofdata.

Example 12 includes the system of example 8, wherein the first storageis a main storage and the second storage is a victim storage, the mainstorage and the victim storage located within a level one cache.

Example 13 includes the system of example 8, further including a cachecontroller configured to be coupled to the store queue, the firststorage, the second storage, and the central processing unit via aninterface, the cache controller to obtain the memory operation from thecentral processing unit.

Example 14 includes a method comprising obtaining a memory operationfrom a controller indicating an address and a first set of data,obtaining a second set of data associated with the address from at leastone of a first storage and a second storage, merging the first set ofdata and the second set of data to produce a third set of data, andproviding the third set of data for writing to at least one of the firststorage and the second storage.

Example 15 includes the method of example 14, wherein the memoryoperation is a first memory operation, wherein the address is a firstaddress, further including obtaining a second memory operationindicating a second address and a fourth set of data, and merging thefourth set of data with the third set of data to produce a fifth set ofdata.

Example 16 includes the method of example 15, further including storingthe first address and the second address in a data store.

Example 17 includes the method of example 15, wherein the first storageis a main storage, and wherein the second storage is a victim storage.

Example 18 includes the method of example 14, further includinggenerating error detection code based on the third set of data, theerror detection code to be stored with the third set of data.

Example 19 includes the method of example 14, further includingobtaining a read memory operation indicating to read the second set ofdata.

Example 20 includes the method of example 14, wherein the controller isa cache controller configured to be coupled to a central processing unitinterface to obtain the memory operation from a central processing unit.

Methods and Apparatus to Reduce Read-Modify-Write Cycles for Non-AlignedWrites in Victim Cache

When issuing a write instruction to a multi-banked storage, such a writeinstruction may be transmitted with a corresponding read instruction,regardless of the size of the write instruction, in an attempt toexecute a full read-modify-write cycle of such a write instruction. Forexample, in such an application, a write instruction may be obtained bya CPU indicating to write 128 bits across two 64-bit memory banks,starting at address A0 of the first memory bank. In such an example,though the entirety of both the example memory banks are being written,such an application maintains a read instruction to read the datacurrently stored in the two example memory banks. However, such anapproach is inefficient as twice the processing power (e.g., a write anda read instruction) is needed. Additionally, such an approach does notprovide any control logic and/or processing circuitry to analyze thewrite instruction.

In the example illustrated in FIG. 11A, the main storage 214 and/or thevictim storage 218 may be multi-banked storages. For example, the victimstorage 218 may include sixteen memory banks (e.g., sixteen sub-RAMs),each 64 bits wide. In such an example, in the event the cache controller220 transmits a write instruction to write all 64 bits of a first bankof the victim storage 218 (e.g., write a 64-bit word starting with thefirst address of the first bank), the write instruction can be executedwithout initiating a read instruction. For example, the bank processinglogic 303 may detect that such a write of an entire bank is to beperformed and, thus, indicate to the cache controller 220 to initiatethe read-modify-write operation, negating to transmit the readinstruction.

Similarly, in the event the cache controller 220 transmits a writeinstruction to write all 128 bits of a first bank and a second bank ofthe victim storage 218 (e.g., a write instruction indicating to write a128 bit word starting with the first address of the first bank andending with the last address of the second bank), the write instructioncan be implemented without initiating a read instruction. For example,the bank processing logic 303 may detect that such a write of theentirety of multiple banks is to be performed and, thus, indicate to thecache controller 220 to initiate the read-modify-write operation,negating to transmit the read instruction.

However, in some examples disclosed herein, the cache controller 220 maytransmit a write instruction to write 130 bits of a first bank, a secondbank, and a third bank of the victim storage (e.g., a write instructionindicating to write a 130 bit work starting with the first address ofthe first bank and ending with the second address of the third bank). Insuch an example, the bank processing logic 303 detects that alladdresses of the first bank and the second bank of the victim storage218 are to be written entirely and, thus, indicate to the cachecontroller to initiate the read-modify-write operations for the firstbank and the second bank of the victim storage, negating to transmit theread instruction. In such an example, the bank processing logic 303 maydetect that the third bank of the victim storage 218 is to be partiallywritten (e.g., two addresses of the 64 addresses are to be written),and, thus, indicate to the cache controller 220 to initiate a fullread-modify-write operation of the third bank of the victim storage 218.Example description of a read-modify-write operation is described above.

Aggressive Write Merging to Reduce Bank Pressure in Victim Cache

In the example of FIG. 11A, the example victim cache store queue 216stores a number of write operations at different sections of the victimcache store queue 216 (e.g., at the example latches 1102 a-e). Forexample, when the CPU 102 transmits three separate write operations in arow, the first write operation that the CPU 102 provided is stored atthe first latch 1102 b and moved to the second latch 1102 c when thesecond operation is received at the first latch 1102 b. Accordingly,after the three write operations are received, the first latch 1102 bwill store and/or output the last write operation with respect to time(e.g., which is last to be stored in the victim storage 218), the secondlatch 1102 c will have the second write operation (e.g., which is secondto be stored in the main storage 214), and the third latch 1102 d willhave the first write operation (e.g., which was the first to be storedin the example victim storage 218). Whenever data in the victim cachestore queue 216 is next to be stored in the victim storage 218, theexample arbitration manager 1114 reserves a cycle for the data to bewritten into the example victim storage 218. Accordingly, during thereserved cycle, the victim storage 218 may not be available to cannotperform read operations. However, if the data operations stored in twoor more of the latches 1102 b, 1102 c, 1102 d correspond to the samememory address, the data can be merged in order to write the data intothe memory address of the victim storage 218 once, instead of two orthree times. For example, if the write operation stored in the latch1102 d corresponds to writing a byte of the memory address and the writeoperation stored in the latch 1102 c corresponds to writing a differentbyte to the memory address, the second write will overwrite the firstwrite.

Instead of reserving a cycle to write the first byte into the victimstorage 218, which will be overwritten in a subsequent cycle, the victimcache store queue 216 merges the two writes into one write, so that onlyone cycle is used to write the second transaction (e.g., to avoidreserving a cycle for the first write). Such an aggressive merge reducesthe number of cycles reserved for write operations. In this manner, thevictim storage 218 will have extra cycles to perform read operations,thereby decreasing the latency of the overall systems.

To enable an aggressive merge of write operations to the same memoryaddress. the output of the example latches 1102 b-1102 d are coupled tothe example merging circuits 1103 a-403 c. For example, the output ofthe third latch 1102 d may be coupled to the merging circuit 1103 a, theoutput of the second latch 1102 c may be coupled to the merging circuit1103 b, and the output of the first latch 1102 b may couple to themerging circuit 1103 c. The output of the merging circuit 1103 a mayadditionally be coupled to the output of the second latch 1102 c and themerging circuit 1103 b, the merging circuit 1103 b may be coupled to themerging circuit 1103 c, and the merging circuit 1103 c may be coupled tothe input of the first latch 1102 b. Additionally or alternatively,there may be additional comparator circuits that compare outputs of adifferent set of latches (e.g., a comparator circuit to compare theoutput of latch 1102 b with the output of latch 1102 d). The examplemerging circuits 1103 a-c include example comparator(s) 1120 and exampleswitches 1122.

The comparator(s) 1120 compare the memory address locations for eachwrite operation that is stored in the respective laches 1102 b-1102 d todetermine whether any of the write operations in the example store queuecorrespond to the same memory address. The example comparator 1120 maybe one comparator to compare all the write operations of the latches1102 b-1102 d or may be separate comparators 1120, to compare two of thelatches 1102 b-d (e.g., a first comparator to the memory address oflatch 1102 b to the memory address of latch 1102 c, a second comparatorto the memory address of 1102 b to the memory address of latch 1102 d,etc.). The comparator(s) 1120 output the results of the comparisons(e.g., with one or more signals corresponding to the one or morecomparisons) to the example switch(es) 1122 and/or the arbitrationmanager 1114. If the example arbitration manager 1114 receives a signalindicative of a match, the arbitration manager 1114 will not reserve thecycle for a first write operation while the first write operation ismerged with a second write operation to the same memory location (e.g.,to free up cycles for other cache operations).

The example switch(es) 1122 reroute the write operations in the examplelatches 1102 b-1102 d based on the comparison. For example, if thememory address of the write operation stored in the example latch 1102 dis the same as the memory address stored in the latch 1102 c, theexample switch(es) 1122 enable and/or disable to reroute the output ofthe latch 1102 d to latch 1102 c, instead of routing to the examplearbitration manager 1114. In this manner, the two write operations arecombined and written into the victim storage 218 in a subsequent cycleas a single write operation instead of two write operations. Theswitch(es) 1122 may be electrical switches, transistors (e.g., MOSFETS),demultiplexers, and/or any other component that can reroute a signal ina circuit.

When a latch receives a rerouted write operation, a MUX of the one ofthe merging circuits 403 a-c (e.g., as further described above inconjunction with FIG. 4D) performs a merging protocol for the one ormore rerouted write operations that prioritizes the newest writeoperation. For example, if the comparator(s) 1120 determines that thewrite operation stored in the example latch 1102 c corresponds to thesame memory address as the write operation stored in the example latch1102 d, the switches(es) 1122 reroute the write operation stored in theexample latch 1102 d to the latch 1102 c. In such an example, if thewrite operation in the example latch 1102 c corresponds to writing datato byte0 and byte2 of the memory address and the write operation fromthe latch 1104 d corresponds to writing data to byte0 and byte1, theexample merging circuit 1103 a merges the two write operations to keepthe writing data stored in latch 1102 c (e.g., the write to byte0 andbyte2) and include the write data from latch 1102 d that doesn't overlap(e.g., byte2). In this example, the write data of byte 0 from the latch1104 d is discarded because the data to be written at byte 0 from thelatch 1104 d will be overwritten by the write instructions of the latch1102 c. Accordingly, in the above example, the merged data correspondsto the write data for byte0 from latch 1102 c, the write data for byte1from latch 1104 d, and the write data for byte2 from the latch 1102 c.When a subsequent write operation is added to the victim cache storequeue 216, the merged write data from the latch 1102 c may bemanipulated (e.g., via one of the example blocks 1104, 1106, 1108)and/or pushed to the next latch 1102 d to be stored in the examplevictim storage 218 during a subsequent cycle. An example hardwareimplementation of the merging protocol is further described above inconjunction with FIG. 4C.

Optimized Atomic Operations and Histogram Operations Support in L1 inVictim Cache

Atomic operations are further example of multi-part memory operations.For example, an atomic compare and swap operation manipulates a valuestored in the memory location based on the results of a comparison ofthe existing value stored at the memory location. For example, the CPU102 may want to replace the data stored in the L1 cache 110 with a newvalue if the existing value stored in the L1 cache 110 matches aspecific value.

In some example systems, when a CPU wanted to perform an atomicoperation, the CPU sent a read operation to a memory address, performedthe manipulation on the read data, and then executed a write operationto the same memory address to store the manipulated data. Additionally,in such systems, the L1 cache may need to paused, rejected, blocked,and/or halted any transactions from other devices (e.g., other cores ofthe CPU, higher level cache, the extended memory, etc.) until the atomicoperation was complete (e.g., to avoid manipulation of the memoryaddress corresponding to the atomic operation during the atomicoperation). Accordingly, such example techniques may require lots ofeffort on behalf of the CPU and lots of reserved cycles that increaselatency.

In the example of FIG. 11A, the example victim cache store queue 216handles atomic operations in conjunction with the read modify writestructure. In this manner, the example CPU 102 can send a single atomicoperations operation to the L1 cache 110, and the victim cache storequeue 216 handles the atomic data manipulation and writing operation.Accordingly, the CPU 102 utilizes a single cycle to execute an atomicoperation and can use the other cycles (e.g., used in atomic protocols)to perform other functions, thereby reducing the latency of the overallcomputing system 100.

In operation, when the CPU 102 transmits an atomic operation and/or anatomic compare and swap operation to increment and/or swap the data at amemory address by a value of 1, for example, the atomic instruction isreceived by the latch 1102 a and the tag RAM 210 verifies whether thememory address is stored in the example victim storage 218. If thememory address is stored in the example victim storage 218, the tag RAM210 instructs the example victim storage 218 to output the data at thememory address while the atomic instructions are passed to the examplelatch 1102 b. While the victim storage 218 outputs the data to the latch324 a, the example latch 1102 b outputs the atomic operation to thelatch 1102 c. At this point the ECC logic 312 performs error detectionand/or correction protocol as described above, and the data from thememory address location is forwarded to the example arithmetic component1104 (e.g., for atomic operations) or the atomic compare component 1106(e.g., for the atomic compare and swap operations). The arithmeticcomponent 1104 obtains the atomic operation (e.g., including dataidentifying how to manipulate the data) and/or the atomic compare andswap 1106 obtains the atomic compare and swap operation (e.g., includinga key and data to be written if the key matches read data) from thelatch 1102 c and obtains the data from the corresponding memory addressfrom the output of the ECC logic 312. The arithmetic component 1104performs the manipulation to the data (e.g., increment the data by 1)and/or the atomic compare component 1106 may perform the swap (replacesthe data if the read data matches a key, etc.) and outputs theincremented and/or swapped-in and outputs the incremented data for thecorresponding memory address (e.g., the atomic result) to the examplelatch 1102 d via the example MUX 1110. (e.g., which is enabled via thecache controller 220). The latch 1102 d outputs the new datacorresponding to the memory address to the ECC generator 1112 togenerate the ECC bit and the arbitration manager 1114 writes the newdata (e.g., the atomic result and/or atomic compare and swap result) tothe memory address in conjunction with the ECC bit in the example victimstorage 218. Additionally or alternatively, the corrected value out ofthe EDD logic 1112 is returned to the CPU 102. Thus, the atomicoperation is performed with only one instruction from the CPU 102.

The atomic compare component 1106 and/or the arithmetic component 1104have several inputs. For example, the atomic component 1106 receives(e.g., obtains) the type of atomic to perform (e.g. atomic compare andswap, or atomic swap), the new data to swap in, the ECC corrected dataread out the of the cache 310, and the size of the size of the data tobe manipulated during the atomic operation (e.g., 32-bit or 64-bit), Inthe example circuit implementation 450 of FIG. 4B, the atomic comparecomponent 1106 receives an atomic compare and swap operation and thearithmetic component 1104 receives an atomic operation. The atomiccompare component 1106 compares the comparison value (e.g., a key)provided by the CPU 102 against the ECC data 310. On a match, the newdata is swapped in place of the old data (e.g. ECC data 310) and outputto the MUX 1110. The size of the new data swapped-in is determined bycas_acc_sz input (e.g. 32-bit or 64-bit). In the example circuitimplementation 450 of FIG. 4C, the atomic compare component 1106 mayalso receive an atomic swap operation. The atomic compare component 1106will swap-in the new data replacing the ECC data 310 regardless of thecomparison result and output the new value to the mux 1110 and the olddata from the address is read from the main storage 214 and is providedback to the CPU 102. The size of the new data swapped-in is determinedby cas_acc_sz input (e.g. 32-bit or 64-bit). In the example circuitimplementation 450 of FIG. 4C, the arithmetic component 1104 may alsoreceive an atomic operation. The arithmetic component 1104 willmanipulate the ECC data 310 and store the manipulated data in the mainstorage element 214. The size of the new data swapped-in is determinedby cas_acc_sz input (e.g. 32-bit or 64-bit). A histogram operation iswhere the CPU 102 wants to know the value of a bin stored many of eachvalue is present in a section of victim storage 218 (e.g., a SRAM linefrom the SRAM portion of the victim storage 218). For example, if a SRAMline has 6 bins with the first bin storing 0, the second bin storing 0,the third bin storing 2, the fourth bin storing 0, the fifth bin storing0, and the sixth bin storing 3. A histogram of the SRAM line maycorrespond to [0, 0, 2, 0, 0, 3]. Alternatively, the histogram may bestructured in a different manner (e.g., [3, 0, 0, 2, 0, 0). In someexample systems, to perform a histogram function, the CPU has to readeach individual value and increment for each value. For example, todetermine how many 0s are stored in a 10 byte SRAM line, the CPU willperform 10 reads. Then to determine how many 1s are in the same 10 byteSRAM line with 10 bins, the CPU will perform an additional 10 reads.Thus, to perform a histogram operation such system may need to perform(N)(M) reads, where N is the size of the section of memory (e.g., 10bytes) being read and M is the number of values that could be store ineach byte. Like an atomic operation, the L1 SRAM may have to block,pause, halt, discard, etc. all other read and/or write operations untilthe histogram operation is complete.

In the example of FIG. 11A, the CPU 102 instructs the victim storage 218to perform the histogram operation. Thereby changing the number ofcycles that the CPU 102 has to reserve for the operation from (N)(M)to 1. Additionally, because the atomic operation protocol is alreadyimplemented in the store queue, the histogram operation can be performedusing the arithmetic component 1104 by performing N reads for the N sizeof the memory and incrementing a count for each value in the examplevictim SRAM store queue 216, thereby reducing the number or readoperation from (N)(M) operations to N operations.

In operation, when the CPU 102 transmits a histogram operationcorresponding to a section (e.g., a SRAM line) of the victim storage218, the operation is stored in the example latch 1102 a while the tagRAM 210 verifies whether the memory address corresponding to thehistogram operation is available in the victim storage 218. The examplecache controller 220 facilitates the read operation for each byte of thesection identified in the histogram operation (e.g., where histogrambins are accessed in parallel by reading up to 128 Bytes at the sametime). If available, the tag RAM 210 instructs the victim storage 218 tooutput the data at a first byte of the section of the victim storage 218while the histogram operation is output by the example latch 1102 a tothe example latch 1102 b. When the example victim storage 218 outputsthe data that has been read from the memory address to the example latch324 a, the latch 1102 b outputs the histogram operation to the examplelatch 1102 c. After the ECC logic 312 performs the error detection andcorrection functionality, the data read at the byte is sent to theexample arithmetic component 1104.

After receiving the read value from the ECC logic 312 and the histograminstructions from the latch 1102 c, the arithmetic component 1104initiates data representative of the histogram. For example, thearithmetic component 1104 may initiate a vector (e.g., representing ahistogram) with an initial value (e.g., zero) for each possible valuethat could be stored in the bytes of the victim storage. The arithmeticcomponent 1104 increments the value of the vector based on output by theECC logic 312 (e.g., the read byte). For example, if the read value ofthe byte is 0, the arithmetic component 1104 increments the valuecorresponding to 0 in the vector.

Because each vector is incremented in parallel, the resulting vectorcorresponds to a histogram of the values that were read in thecorresponding sections of SRAM in parallel. Because a value of thehistogram is incremented for each bit, the resulting vector is ahistogram of the values stored in the section of memory identified inthe histogram operation from the CPU 102. In some examples, thearithmetic component 1104 may increment in parallel by some weightedvalue (e.g., 1.5). When complete, the example histogram is input to theexample MUX 418 (e.g., controlled by the example pending store addresstable 1116) to be input to the MUX 316 via the example latch 1102 e.Once the operation is complete, the example cache controller 220controls the MUX 316 to output the final histogram vector to the exampleCPU interface 202 via the multiplexer circuit 314 and the example latch322 b, thereby ending the histogram operation.

In some examples, the L1 cache 110 supports functionality where ahistogram bin can saturate after the histogram bin includes more than athreshold limit of the bin size (e.g., a byte, a halfword, a word,etc.). The above Table 1 illustrates an example of saturation values.Using this functionality, the histogram bin values will not roll overonce they reach the maximum value.

Example methods, apparatus, systems, and articles of manufacture tofacilitate victim cache and atomic operations are disclosed herein.Further examples and combinations thereof include the following: Example1 includes a system comprising a first cache storage to store a firstset of data, a second cache storage to store a second set of data thathas been evicted from the first cache storage, and a storage queuecoupled to the first cache storage and the second cache storage, thestorage queue including an arithmetic component to receive the secondset of data from the second cache storage in response to a memoryoperation, and perform an arithmetic operation on the second set of datato produce a third set of data, and an arbitration manager to store thethird set of data in the second cache storage.

Example 2 includes the system of example 1, wherein the first cachestorage is a main storage and the second cache storage is a victimstorage.

Example 3 includes the system of example 1, wherein the arithmeticcomponent to obtain (a) the second set of data from the second cachestorage via an error detection and correction circuit and (b) the memoryoperation from a central processing unit via a latch.

Example 4 includes the system of example 1, wherein the third set ofdata is stored in the second cache storage with a single instructionfrom a central processing unit at a single cycle.

Example 5 includes the system of example 1, further including amodified, exclusive, shared, invalid (MESI) component to determine astate of a memory address included in the memory operation, and aninterface to, if the memory address included in the memory operationcorresponds to a shared state, send miss instructions to another cache,the miss instructions including an exclusive state request.

Example 6 includes the system of example 5, wherein the arbitrationmanager is to store the third set of data at the memory address in thesecond cache storage after the exclusive state request has been grantedfrom the other cache.

Example 7 includes the system of example 5, wherein the arithmeticcomponent is to receive the second set of data from the second cachestorage after the exclusive state request has been granted from theother cache.

Example 8 includes the system of example 5, wherein the second cachestorage and the first cache storage are connected in parallel to acentral processing unit.

Example 9 includes the system of example 5, wherein the memory operationis an atomic operation.

Example 10 includes a storage queue comprising an arithmetic componentto receive a second set of data from a cache storage in response to amemory operation, and perform an arithmetic operation on the second setof data to produce a third set of data, and an arbitration manager tostore the third set of data in the cache storage.

Example 11 includes the storage queue of example 10, wherein the cachestorage is a victim cache storage, the victim cache storage storing datathat has been removed from a main cache storage.

Example 12 includes the storage queue of example 11, wherein the victimcache storage and the main cache storage are connected in parallel to acentral processing unit.

Example 13 includes the storage queue of example 10, wherein thearithmetic component to obtain (a) the second set of data from the cachestorage via an error detection and correction circuit and (b) the memoryoperation from a central processing unit via a latch.

Example 14 includes the storage queue of example 10, wherein the thirdset of data is stored in the cache storage with a single instructionfrom a central processing unit at a single cycle.

Example 15 includes the storage queue of example 10, wherein thearbitration manager is to store the third set of data at a memoryaddress in the cache storage after an exclusive state request has beengranted from another other cache.

Example 16 includes the storage queue of example 15, wherein thearithmetic component is to receive the second set of data from the cachestorage from the memory address after the exclusive state request hasbeen granted from the other cache.

Example 17 includes the storage queue of example 10, wherein the memoryoperation is an atomic operation.

Example 18 includes a method comprising obtaining a second set of datafrom a cache storage in response to a memory operation, and performingan arithmetic operation on the second set of data to produce a third setof data, and storing store the third set of data in the cache storage.

Example 19 includes the method of example 18, wherein the cache storageis a victim cache storage, the victim cache storage storing data thathas been removed from a main storage.

Example 20 includes the method of example 19, further including storingthe third set of data at a memory address in the cache storage after anexclusive state request has been granted from another other cache AtomicCompare and Swap Support in L1 in Victim Cache for Coherent System

If data from an address is stored in the L1 cache 110, data for the sameaddress may also be cached in other caches (e.g., L2 cache 112, and/orL3 cache 114). Accordingly, the memory address needs to be trackedand/or monitored to ensure that any changes to the data in one cache isidentified, tracked, and/or reflected to the other caches (e.g., L2cache 112 and L3 cache 114). As described above in conjunction withFIGS. 3A-3D, the example MESI RAM 300 tracks the state of the datastored in the victim storage 218 to be able to avoid issues withmismatched data in different caches that correspond to the same memoryaddress. For example, if the CPU 102 transmits a read operation, theexample MESI RAM 300 changes the state of the memory address to shared,because the data in the memory address will not be manipulated. If theCPU 102 transmits a write operation, the example MESI RAM 300 changesthe state of the memory address to exclusive, because the data in thememory address will be manipulated and the victim storage 218 needswrite permission for the address. After the data in the memory addressis written to the victim storage 218, the MESI RAM 300 updates the stateof the memory address to modified (e.g., indicating that the memoryaddress has been modified).

As described above, during atomic and/or histogram protocols, the datafrom a memory address is read from the victim storage 218 and providedto the victim cache store queue 216 to be updated (e.g., incremented)and written back into the victim storage 218. However, if the MESI RAM300 has identified the state of the corresponding memory address as inshared state, the write operation of the atomic protocol may causeproblems with other level caches (e.g., because the write will cause amismatch of data in different caches).

To avoid such data mismatches during atomic operations (e.g., includingatomic compare and swap), the example cache controller 220 marks cachehits that correspond to a shared state as a cache miss. In this manner,the cache controller 220 can instruct the L2 interface 228 to send thecache miss to the higher level cache with an exclusive state request. Inthis manner, the higher level cache can grant the exclusive state to theL1 cache 110 and the L1 cache 110 can perform the read and writeoperation as part of the atomic operation in response to receiving thegranted exclusive state.

After the cache miss with exclusive request is sent to the higher levelcache and the higher level cache responds with the write data and theexclusive response, the example atomic operation logic 1106 willinstruct the MESI RAM 300 to tag the data as modified. The received datafrom the L2 cache 112 is transmitted into the victim cache store queue216 to be stored in the victim storage 218. Because the operation was anatomic operation (e.g., a regular atomic operation or an atomic compareand swap) or a histogram protocol, the data from the higher level cacheis manipulated by the example arithmetic component 1104 and/or theexample atomic compare component 1106 for the manipulation and stored inthe example victim storage 218 via the example ECC generator 1112 andthe example arbitration manager 1114.

While an example manner of implementing the L1 data cache 110 of FIG. 1is illustrated in FIGS. 2-5 and/or 10-11, one or more of the elements,processes and/or devices illustrated in FIGS. 2-5 and/or 10-11 may becombined, divided, re-arranged, omitted, eliminated and/or implementedin any other way. Further, the example CPU interface 202, the exampletag RAM accesses 204, 206, the example tag RAM 208, 210, the examplemain cache store que 212, the example main storage 214, the examplevictim cache store queue 216, the example victim storage 218, theexample cache controller 220, the example main cache controller 222, theexample victim cache controller 224, the example L2 interface 228, theexample MESI RAM 300, the example address processing components 302 a-c,the example bank processing logic 303, the example hit-miss comparisonlogic 304, 306, the example replacement policy component 208, theexample ECC logic 310, the example MUX circuit 314, 316, 318, 320, 330,330 a-c, 410, 418, 508 the example latches 322 a, 324 a, 402 a-d,1102-a-d, the example address encoder 326, 326 a, 326 b, 328, 328 a, 328b the example address read 332, the example merging circuits 403 a-c,1103 a-c, the example arithmetic component 404, 1104 the example atomiccompare component 406, 1106, the example RMW component 408, 1108, theexample ECC generator 412, 1112, the example arbitration manager 414,1114, the example pending store address database 416, 1116, the examplecomparator 420, 1120, the example switches 422, 1122, the example ports424, 426,1124, 1126 the interfaces 502, 504, the example address 506,and/or more generally the L1 data cache 110 of FIGS. 2-5 and/or 10-11may be implemented by hardware, software, firmware and/or anycombination of hardware, software and/or firmware. Thus, for example,any of the example CPU interface 202, the example tag RAM accesses 204,206, the example tag RAM 208, 210, the example main cache store que 212,the example main storage 214, the example victim cache store queue 216,the example victim storage 218, the example cache controller 220, theexample main cache controller 222, the example victim cache controller224, the example L2 interface 228, the example MESI RAM 300, the exampleaddress processing components 302 a-c, the example bank processing logic303, the example hit-miss comparison logic 304, 306, the examplereplacement policy component 208, the example ECC logic 310, the exampleMUX circuit 314, 316, 318, 320, 330, 330 a-c, 410, 418, 508 the examplelatches 322 a, 322 b, 324 a, 322 b, 402 a-d, 1102-a-d, the exampleaddress encoder 326, 326 a, 326 b, 328, 328 a, 328 b the example addressread 332, the example merging circuits 403 a-c, 1103 a-c, the examplearithmetic component 404, 1104 the example atomic compare component 406,1106, the example RMW component 408, 1108, the example ECC generator412, 1112, the example arbitration manager 414, 1114, the examplepending store address database 416, 1116, the example comparator 420,1120, the example switches 422, 1122, the example ports 424, 426,1124,1126 the interfaces 502, 504, the example address 506, and/or moregenerally the L1 data cache 110 of FIGS. 2-5 and/or 10-11 could beimplemented by one or more analog or digital circuit(s), logic circuits,programmable processor(s), programmable controller(s), graphicsprocessing unit(s) (GPU(s)), digital signal processor(s) (DSP(s)),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example CPU interface 202, the example tag RAM accesses 204, 206,the example tag RAM 208, 210, the example main cache store que 212, theexample main storage 214, the example victim cache store queue 216, theexample victim storage 218, the example cache controller 220, theexample main cache controller 222, the example victim cache controller224, the example L2 interface 228, the example MESI RAM 300, the exampleaddress processing components 302 a-c, the example bank processing logic303, the example hit-miss comparison logic 304, 306, the examplereplacement policy component 208, the example ECC logic 310, the exampleMUX circuit 314, 316, 318, 320, 330, 330 a-c, 410, 418, 508 the examplelatches 322 a, 322 b, 324 a, 324 b, 402 a-d, 1102-a-d, the exampleaddress encoder 326, 326 a, 326 b, 328, 328 a, 328 b, the exampleaddress read 332, the example merging circuits 403 a-c, 1103 a-c, theexample arithmetic component 404, 1104 the example atomic comparecomponent 406, 1106, the example RMW component 408, 1108, the exampleECC generator 412, 1112, the example arbitration manager 414, 1114, theexample pending store address database 416, 1116, the example comparator420, 1120, the example switches 422, 1122, the example ports 424,426,1124, 1126 the interfaces 502, 504, the example address 506, and/ormore generally the L1 data cache 110 of FIGS. 2-5 and/or 10-11 is/arehereby expressly defined to include a non-transitory computer readablestorage device or storage disk such as a memory, a digital versatiledisk (DVD), a compact disk (CD), a Blu-ray disk, etc. including thesoftware and/or firmware. Further still, the example L1 data cache 110of FIG. 1 may include one or more elements, processes and/or devices inaddition to, or instead of, those illustrated in FIGS. 2-5 and/or 10-11,and/or may include more than one of any or all of the illustratedelements, processes and devices. As used herein, the phrase “incommunication,” including variations thereof, encompasses directcommunication and/or indirect communication through one or moreintermediary components, and does not require direct physical (e.g.,wired) communication and/or constant communication, but ratheradditionally includes selective communication at periodic intervals,scheduled intervals, aperiodic intervals, and/or one-time events.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the L1 data cache of FIGS. 1-5and/or 10-11 is shown in FIGS. 12-33. The machine readable instructionsmay be one or more executable programs or portion(s) of an executableprogram for execution by a computer processor such as the processor 3412shown in the example processor platform 3400 discussed below inconnection with FIG. 34. The program may be embodied in software storedon a non-transitory computer readable storage medium such as a CD-ROM, afloppy disk, a hard drive, a DVD, a Blu-ray disk, or a memory associatedwith the processor 3412, but the entire program and/or parts thereofcould alternatively be executed by a device other than the processor3412 and/or embodied in firmware or dedicated hardware. Further,although the example program is described with reference to theflowchart illustrated in FIG. 34, many other methods of implementing theexample L1 cache 110 may alternatively be used. For example, the orderof execution of the blocks may be changed, and/or some of the blocksdescribed may be changed, eliminated, or combined. Additionally oralternatively, any or all of the blocks may be implemented by one ormore hardware circuits (e.g., discrete and/or integrated analog and/ordigital circuitry, an FPGA, an ASIC, a comparator, anoperational-amplifier (op-amp), a logic circuit, etc.) structured toperform the corresponding operation without executing software orfirmware.

The machine readable instructions described herein may be stored in oneor more of a compressed format, an encrypted format, a fragmentedformat, a compiled format, an executable format, a packaged format, etc.Machine readable instructions as described herein may be stored as data(e.g., portions of instructions, code, representations of code, etc.)that may be utilized to create, manufacture, and/or produce machineexecutable instructions. For example, the machine readable instructionsmay be fragmented and stored on one or more storage devices and/orcomputing devices (e.g., servers). The machine readable instructions mayrequire one or more of installation, modification, adaptation, updating,combining, supplementing, configuring, decryption, decompression,unpacking, distribution, reassignment, compilation, etc. in order tomake them directly readable, interpretable, and/or executable by acomputing device and/or other machine. For example, the machine readableinstructions may be stored in multiple parts, which are individuallycompressed, encrypted, and stored on separate computing devices, whereinthe parts when decrypted, decompressed, and combined form a set ofexecutable instructions that implement a program such as that describedherein.

In another example, the machine readable instructions may be stored in astate in which they may be read by a computer, but require addition of alibrary (e.g., a dynamic link library (DLL)), a software development kit(SDK), an application programming interface (API), etc. in order toexecute the instructions on a particular computing device or otherdevice. In another example, the machine readable instructions may needto be configured (e.g., settings stored, data input, network addressesrecorded, etc.) before the machine readable instructions and/or thecorresponding program(s) can be executed in whole or in part. Thus, thedisclosed machine readable instructions and/or corresponding program(s)are intended to encompass such machine readable instructions and/orprogram(s) regardless of the particular format or state of the machinereadable instructions and/or program(s) when stored or otherwise at restor in transit.

The machine readable instructions described herein can be represented byany past, present, or future instruction language, scripting language,programming language, etc. For example, the machine readableinstructions may be represented using any of the following languages: C,C++, Java, C#, Perl, Python, JavaScript, HyperText Markup Language(HTML), Structured Query Language (SQL), Swift, etc.

As mentioned above, the example processes of FIGS. 12-33 may beimplemented using executable instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

“Including” and “comprising” (and all forms and tenses thereof) are openended terms. Thus, whenever a claim employs any form of “include” or“comprise” (e.g., comprises, includes, comprising, including, having,etc.) as a preamble or within a claim recitation of any kind, additionalelements, terms, etc. may be present without falling outside the scopeof the corresponding claim or recitation. As used herein, when thephrase “at least” is used as the transition term in, for example, apreamble of a claim, it is open-ended in the same manner as the term“comprising” and “including” are open ended. The term “and/or” whenused, for example, in a form such as A, B, and/or C refers to anycombination or subset of A, B, C such as (1) A alone, (2) B alone, (3) Calone, (4) A with B, (5) A with C, (6) B with C, and (7) A with B andwith C. As used herein in the context of describing structures,components, items, objects and/or things, the phrase “at least one of Aand B” refers to implementations including any of (1) at least one A,(2) at least one B, and (3) at least one A and at least one B.Similarly, as used herein in the context of describing structures,components, items, objects and/or things, the phrase “at least one of Aor B” refers to implementations including any of (1) at least one A, (2)at least one B, and (3) at least one A and at least one B. As usedherein in the context of describing the performance or execution ofprocesses, instructions, actions, activities and/or steps, the phrase“at least one of A and B” refers to implementations including any of (1)at least one A, (2) at least one B, and (3) at least one A and at leastone B. Similarly, as used herein in the context of describing theperformance or execution of processes, instructions, actions, activitiesand/or steps, the phrase “at least one of A or B” refers toimplementations including any of (1) at least one A, (2) at least one B,and (3) at least one A and at least one B.

As used herein, singular references (e.g., “a”, “an”, “first”, “second”,etc.) do not exclude a plurality. The term “a” or “an” entity, as usedherein, refers to one or more of that entity. The terms “a” (or “an”),“one or more”, and “at least one” can be used interchangeably herein.Furthermore, although individually listed, a plurality of means,elements or method actions may be implemented by, e.g., a single unit orprocessor. Additionally, although individual features may be included indifferent examples or claims, these may possibly be combined, and theinclusion in different examples or claims does not imply that acombination of features is not feasible and/or advantageous.

FIG. 12 is an example flowchart representative of example machinereadable instructions 1200 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform write miss caching in the example victimstorage 218 as described above. Although the instructions of FIG. 12 aredescribed in conjunction with the L1 cache 110 of FIGS. 1-5, theinstructions may be described in conjunction with any type of storage inany type of cache.

At block 1202, the example cache controller 220 allocates a section ofthe victim storage 218 for write miss information (e.g., a write misscache). As described above, the write miss information corresponds towhen the CPU 102 transmits write instructions to the example L1 cache110 to a memory address that is not stored in the storages 214, 218 ofthe L1 cache 110 (e.g., so the write instructions are sent to higherlevel cache for execution). At block 1204, the cache controller 220accesses the output of the example hit/miss logic 304, 306 to determineif a current write operation from the CPU 102 (e.g., received by thecache controller 220) resulted in a write miss (e.g., the memory addressfrom the write operation is not stored in the example storages 214,218). In some examples, where the operation from the CPU 102 missed themain storage 214 but hit the victim storage 218, the hit miss comparisonlogic 304 may transmit a write miss to the example victim storage 218.In such an example, the victim storage 218 discards the write missinformation because the operation hit the victim storage 218.

If the cache controller 220, after interfacing with the one or more ofthe example tag RAMs 208, 210, determines that a current write operationfrom the CPU 102 did not result in a write miss (block 1204: NO),control returns to block 1204 until a write operation results in a writemiss. If the cache controller 220 determines that a current writeoperation from the CPU 102 results in a write miss (block 1204: YES),the example cache controller 220 determines if the write missinformation corresponds to the same memory address as any write missinformation already stored in the allocated section (block 1206). If theexample cache controller 220 determines that the write miss informationcorresponds to the same memory address as any write miss informationalready stored in the allocated section (block 1206: YES), the cachecontroller 220 instructs the example victim storage 218 to merge thewrite miss information with the stored write miss informationcorresponding to the same memory address (block 1208). The examplevictim storage 218 merges the two write miss information by overwritingthe older write miss information with the most recent write missinformation when the most recent write miss information overlaps (e.g.,corresponds to the same bytes as) the older write miss information(e.g., discarding the older write miss information that overlaps themore recent write miss information) and maintaining the older write missinformation that does not overlap the more recent write missinformation.

If the example cache controller 220 determines that the write missinformation does not correspond to the same memory address as any writemiss information already stored in the allocated section (block 1206:NO), the cache controller 220 stores, in the example victim storage 218,the write miss information in the allocated section (block 1210).

At block 1212, the example cache controller 220 determines if more thana threshold amount of write miss information has been stored in theallocated section. The threshold amount may be set to the size of thevictim cache (e.g., the threshold is satisfies when the allocatedsection is full), the size of the L2 interface 228 (e.g., if the L2interface has a 64 byte bandwidth, then the threshold is set to 64bytes), and/or any other amount set by a user and/or manufacturer. Ifthe example cache controller 220 determines that more than the threshold(e.g., a first threshold) amount of write miss information has not beenstored in the allocated section (block 1212: NO), control returns toblock 1204.

If the example cache controller 220 determines that more than thethreshold amount of write miss information has been stored in theallocated section (block 1212: YES), the cache controller 220 selects athreshold (e.g., a second threshold) amount of write miss information(e.g., the N oldest write miss information stored in the allocatedsection where N corresponds to the threshold) from the allocated sectionof the victim storage 218 (block 1214). The second threshold maycorrespond to (e.g., be the same as) the first threshold and/or maycorrespond to the bandwidth of the L2 interface 228 (e.g., if thebandwidth of the L2 interface 228 is 64 bytes, than no more than 64bytes of write miss data is selected). Additionally or alternatively,the cache controller 220 may proceed to block 1210 when a thresholdamount of time has occurred. At block 1216, the cache controller 220causes the example victim storage 218 to remove the selected write missinformation from the allocated section. At block 1218, the example L2cache interface 228 transmits the selected write miss information to thehigher level cache (e.g., the L2 cache 112). As described above, sendingmultiple write miss information to utilize more of the bandwidth of theL2 interface 112 results in a more efficient system.

FIG. 13 is an example flowchart representative of example machinereadable instructions 1300 that may be executed by the example L1 cache110 of FIGS. 1-5 to facilitate a read-modify-write operation, inconjunction with the above Section 2. In FIG. 13, the main cache storequeue 212 obtains a write instruction transmitted by the CPU 102 (e.g.,transmitted through the cache controller 220) indicating byte(s) of aword, or an entire word, to be re-written. (Block 1302). In someexamples disclosed herein, the write port 426 may obtain the writeinstruction transmitted by the CPU 102.

At block 1304, the main cache store queue 212 transmits the value of theportion of the word to be rewritten to the latch 402 b. (Block 1304). Insome examples, the latch 402 b transmits the value of the portion of theword to be rewritten to the latch 402 c.

At block 1306, the main cache store queue 212 stores the address valueassociated with the location of the portion of the word to be rewrittenin the pending store address data store 416. (Block 1306). Additionally,the tag ram 208 transmits a read instruction (e.g., a read request) ofthe entire currently stored word to the main storage 214. (Block 1308).At block 1310, the main cache store queue 212 determines whether therehas been a subsequent clock cycle of the CPU 102, or the cachecontroller 220. (Block 1310). In some examples disclosed herein, thelatch 402 c determines whether there has been a subsequent clock cycleof the CPU 102, or the cache controller 220. In response to determiningthat there has not been a subsequent clock cycle of the CPU 102, or thecache controller 220, (e.g., the control of block 1310 returns a resultof NO), the process waits.

Alternatively, in response to determining that there has been asubsequent cycle of the CPU 102, or the cache controller 220, (e.g., thecontrol of block 1310 returns a result of YES), the read-modify-writemerge component 408 obtains the value of the portion of the word (e.g.,the byte) stored in the latch 402 c. (Block 1312). Additionally, theread-modify-write merge component 408 obtains the entire currentlystored word transmitted by the ECC logic 310. (Block 1314). In thismanner, the read-modify-write merge 408 identifies the address of thebyte in the currently stored word to be updated. Once theread-modify-write merge component 408 identifies and/or otherwiseobtains (a) the value (e.g., byte value, bit value, etc.) of the portionof the currently stored word to be updated from the latch 402 c and the(b) currently stored word from the ECC logic 310, the read-modify-writemerge component 408 writes (e.g., replaces) the portion of the currentlystored word with the value of the portion of the currently stored wordobtained from the latch 402 c. (Block 1316).

At block 1318, the main cache store queue 212 generates error detectioncode based on the word, the error detection code to be stored with theword. (Block 1318). In some examples disclosed herein the ECC generator412 generating error detection code based on the word, the errordetection code to be stored with the word.

The control of block 1318 may be performed in response to an additionalsubsequent clock cycle of the CPU 102, or the cache controller 220.

In response, the main cache store queue 212 determines whether anadditional write instruction is obtained. (Block 1322). the event themain cache store queue 212 determines another write instruction isobtained (e.g., the control of block 1322 returns a result of YES), theprocess returns to block 1302. Alternatively, in the event the maincache store queue 212 determines another write instruction is notobtained (e.g., the control of block 1322 returns a result of NO), theprocess 1300 may wait until a threshold timeout period occurs, thusending the process 1300.

FIG. 14 is an example flowchart representative of example machinereadable instructions 1400 that may be executed by the example L1 cache110 of FIGS. 1-5 to facilitate a read-modify-write operation fornon-aligned writes, in conjunction with the above-Sections 3 and/or 14.At block 1402, the bank processing logic 303 of FIGS. 3A-3D analyzes thewrite instructions obtained from the CPU 102 (e.g., the writeinstructions obtained via the CPU interface 202). For example, the bankprocessing logic 303 may operate as initial processing circuitry todetermine the nature of the write instruction.

In this manner, the bank processing logic 303 determines the number ofmemory banks to be written to when executing the write instruction.(Block 1404). For example, the bank processing logic 303 determines theaddress locations of the write instruction and, as such, determines thebanks of either the main storage 214 or the victim storage 218 thatinclude the corresponding address locations. In response, the bankprocessing logic 303 determines whether all addresses of a memory bank(e.g., a memory bank included in either the main storage 214 or thevictim storage 218) are to be rewritten. (Block 1406).

In the event the bank processing logic 303 determines all addresses of amemory bank (e.g., a memory bank included in either the main storage 214or the victim storage 218) are to be rewritten (e.g., the control ofblock 1406 returns a result of YES), the bank processing logic 303indicates to the CPU 102, or the cache controller 220, to execute thewrite instruction without reading the currently stored values in thememory bank. (Block 1408). For example, the bank processing logic 303may identify that addresses A0 to A70 are to be rewritten and, thus,determine that the first memory bank (e.g., a memory bank havingaddresses A0 to A63) are to be rewritten. Thus, such a first memory bankcan be rewritten without reading the currently stored values.

Alternatively, in the event the bank processing logic 303 determinesthat all addresses of a memory bank are not being rewritten (e.g., thecontrol of block 1406 returns a result of NO), or in response to theexecution of the control in block 1408, the bank processing logic 303determines whether there are additional memory banks to analyze. (Block1410).

For example, to execute the control of block 1410, the bank processinglogic 303 determines whether all memory banks affected by the writeinstruction have been analyzed. In following the example above, the bankprocessing logic 303 determines that the memory bank including addressesA64 to A70 have not been analyzed. Thus, in the event the bankprocessing logic 303 determines that there is an additional memory bankto analyze (e.g., the control of block 1410 returns a result of YES),the process 1400 returns to block 1406. Alternatively, in the event thebank processing logic 303 determines that there are no additional memorybanks to analyze (e.g., the control of block 1410 returns a result ofNO), the bank processing logic 303 determines whether another writeinstruction is obtained. (Block 1412).

In examples disclosed herein, in the event the bank processing logic 303determines there is another write instruction (e.g., the control ofblock 1412 returns a result of YES), the process 1400 returns to block1402. Alternatively, in the event the bank processing logic 303determines that there is not another write instruction (e.g., thecontrol of block 1412 returns a result of NO), the process 1400 may waituntil a threshold timeout period occurs, thus ending the process 1400.

FIG. 15 is an example flowchart representative of example machinereadable instructions 1500 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform an aggressive write merge in the examplemain cache store queue 212 and/or the victim cache store queue 216, inconjunction with the above sections 4 and/or 15. Although theinstructions of FIG. 15 are described in conjunction with the L1 cache110 of FIGS. 1-5, the instructions may be described in conjunction withany type of storage in any type of cache. The instructions of FIG. 15are described in conjunction with the main cache store queue 212 and themain storage 214. However, the instruction of FIG. 15 can likewise beused in conjunction with the victim cache store queue 216 and the victimstorage 218.

At block 1502, the example comparator(s) 420 of the example mergingcircuits 403 a-c obtains write instructions from corresponding latches402 b-d. As described above, each of the latches 402 b-d includedifferent write instructions from the CPU 102. At block 1504, theexample comparator(s) 420 of the example merging circuits 403 a-ccompare the memory addresses for the write instructions from the latches402 b-d. For example, the comparator 420 of the merging circuit 403 acompares the memory address for the write instructions output by thelatch 402 d with the write instructions output by the latch 402 c. Atblock 1506, the example comparator(s) 420 determine if any two or morewrite instructions output by the latches 402 b-d correspond to the samememory address. If the comparator(s) 420 determine that any two or morewrite instructions output by the latches 402 b-d do not correspond tothe same memory address (block 1506: NO), control continues to block1520, as further described below.

If the comparator(s) 420 determine that any two or more writeinstructions output by the latches 402 b-d corresponds to the samememory address (block 1506: YES), control continues to block 1508. Foreach group of write instructions corresponding to the same memoryaddress (blocks 1508-1514), the one or more of the example mergingcircuit 1103 a-c that receive(s) write instructions for the same memoryaddress maintain(s) the write data for the byte(s) for the newest writeinstructions (e.g., the write instructions that were more recentlyreceived from the CPU 102) that overlap the write data for the samebyte(s) from older write instructions (block 1510). At block 1512, theone or more of the example merging circuit 1103 a that receive(s) writeinstructions for the same memory address update(s) the write data forbyte(s) from older write instructions that do not overlap with writedata from the newest write instructions. For example, if the mergingcircuit 1103 a, storing a write instruction to write byte0 of a memoryaddress, receives rerouted data from latch 402 d, the rerouted datacorresponding to a write instruction to write byte0 and byte 1 of thememory address, then the merging circuit 1103 a maintains the writeinstruction to write to byte0 (e.g., discarding the write instruction towrite byte0 from latch 402 d, because the write instruction is older)and updates the write instruction to write to byte1 corresponding to theinstruction from latch 402 b (e.g., because the instruction does notoverlap with the newest write instructions). At block 1516, the exampleswitch(es) 422 reroute the merged write instructions the latch with thenewest write instructions that also corresponds to the matching memoryaddress (block 1508).

At block 1518, the one or more of the merging circuits 402 a-c thatrerouted write instructions to be merged flags the data that wasrerouted. For example, the one or more merging circuits 403 a-c maytransmit a signal to the example arbitration manager 414 and/or thecache controller 220. In this manner, the arbitration manager 414 and/orthe cache controller 220 can avoid reserving a cycle to write the datathat has be rerouted into a prior latch for merging. At block 1520, thelatch 402 b determines if an additional write instruction has beenreceived. If the latch 402 d determines that an additional instructionhas not been received (block 1520: NO), control returns to block 1520until additional write instructions are received. If the latch 402 ddetermines that an additional instruction has been received (block 1520:YES), control returns to block 1504.

FIG. 16 is an example flowchart representative of example machinereadable instructions 1600 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform an atomic operation, as described above inconjunction with the above Sections 5 and 16. Although the instructionsof FIG. 16 are described in conjunction with the L1 cache 110 of FIGS.1-5, the instructions may be described in conjunction with any type ofstorage in any type of cache. The instructions of FIG. 16 are describedin conjunction with the main half of the L1 cache 110 (e.g., the maincache store queue 212, the main storage 214, etc.). However, theinstruction of FIG. 16 can likewise be used in conjunction with thevictim side of the L1 cache 110 (e.g., the victim cache store queue 216,the victim storage 218, etc.).

At block 1602, the cache controller 220 and/or the example latch 402 aobtains an atomic operation from the CPU 102. When the latch 402 aobtains the atomic operation, the cache controller 220 and and/or thelatch 402 a sends the memory address for the atomic operation to theexample tag RAM 208 to determine whether the data corresponding to theatomic operation is stored in the example main storage 214. At block1604, the cache controller 220 interfaces with the example hit/misslogic 304 to determine if the memory address corresponding to the atomicoperations is stored in the main storage 214.

If the cache controller 220 determines that the memory addresscorresponding to the atomic operation is not stored in the main storage214 (block 1604: NO), cache controller 220 interfaces with the exampleL2 cache interface 228 to submit the atomic miss information to higherlevel cache (e.g., the L2 cache 112 of FIG. 1) (block 1606). In thismanner, the example L2 cache 112 can return the corresponding data fromthe memory address corresponding to be stored in the L1 cache 110 toexecute the atomic operation. The L2 cache 112 may have the datacorresponding to the memory address stored locally or may obtain thedata from the L3 cache 114 and/or the extended memory 110 (e.g., via theL3 cache 114). At block 1608, the example arithmetic component 404 ofthe main cache store queue 212 obtains the data corresponding to thememory address from the L2 cache 112 via the L2 interface 228. Forexample, the data may be stored in the example main storage 214, read,and input to the example arithmetic component 404.

If the cache controller 220 determines that the memory addresscorresponding to the atomic operation is stored in the main storage 214(block 1604: YES), cache controller 220 causes the example arithmeticcomponent 404 to obtain the data corresponding to the memory address ofthe atomic operation from the main storage 214 (block 1610). At block1612, cache controller 220 causes the example arithmetic component 404to perform the atomic operation from the CPU 102 in conjunction with thedata from the storage and/or higher level cache that corresponds to theatomic operation. For example, while blocks 1602-1610 occur, the atomicoperation is sent to the main cache store queue 212 via the latch 402 a.The atomic operation includes the specifics of the operation (e.g.,increment, decrement, etc.). Accordingly, the arithmetic component 404obtains the atomic operation and the data corresponding to the memoryaddress of the atomic operation. Thus, the arithmetic component 404 canperform the atomic operation (e.g., increment, decrement, etc.) usingthe obtained data (e.g., that corresponds to the memory address of theatomic operation). At block 1614, the example cache controller 220controls the MUX 410 (e.g., via the select line) to ensure that theoutput of the arithmetic component 404 is output to the example latch402 d. Accordingly, the manipulated data (e.g., incremented data,decremented data, etc.) can be passed to the example ECC generation 412to generate an ECC code for the manipulated data (block 1616).

At block 1618, the example ECC generation 412 outputs an ECC code forthe manipulated data, the manipulated data, and the memory addresslocation to the example to the example arbitration manager 414. At block1620, the cache controller 220 causes the example arbitration manager414 to store the atomic output (e.g., the manipulated data) in the mainstorage 214 at the memory address of the atomic operation.

FIG. 17 is an example flowchart representative of example machinereadable instructions 1700 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform a histogram operation, in conjunction withthe above Sections 5 and/or 16. Although the instructions of FIG. 17 aredescribed in conjunction with the L1 cache 110 of FIGS. 1-5, theinstructions may be described in conjunction with any type of storage inany type of cache. The instructions of FIG. 17 are described inconjunction with the main half of the L1 cache 110 (e.g., the main cachestore queue 212, the main storage 214, etc.). However, the instructionof FIG. 17 can likewise be used in conjunction with the victim side ofthe L1 cache 110 (e.g., the victim cache store queue 216, the victimstorage 218, etc.).

At block 1702, the cache controller 220 and/or the example latch 402 bof the main cache store queue 212 and/or the example tag RAM 208 obtainsa histogram operation from the CPU 102. As described above, thehistogram operation includes determining a total number of each valuestored in a section of memory (e.g., a SRAM line). At block 1704, thecache controller 220 interfaces with the example hit/miss logic 304 todetermine if the memory address corresponding to the histogram operationis stored in the SRAM of the main storage 214. If the cache controller220 determines that the memory address corresponding to the histogramoperation is stored in the SRAM of the main storage 214 (block 1704:YES), control continues to block 1710.

If the cache controller 220 determines that the memory addresscorresponding to the histogram operation is not stored in SRAM of themain storage 214 (block 1704: NO), the cache controller 220 interfaceswith the example L2 interface 228 to transmit the read miss informationto higher level cache (e.g., the example L2 cache 112) (block 1706). Atblock 1708, the cache controller 220 utilizes the example arbitrationmanager 414 to obtain the read data from the higher level cache via theL2 interface 228 and stores the data corresponding to the memory addressof the histogram operation in the SRAM of the main storage 214. At block1710, the cache controller 220 and/or causes the example arithmeticcomponent 404 to initiate a histogram vector with values to berepresentative of counts for values stored in the section of the SRAM ofthe main storage 214.

At block 1712, the cache controller 220 causes the example SRAM of themain storage 214 outputs the read value of the bins corresponding to thesection of SRAM in parallel. The read values are output to the examplearithmetic component 404 via the ECC logic 310. At block 1714, the cachecontroller 220 utilizes the example arithmetic component 404 toincrement one of the elements of the histogram value based on the readvalues of the bins. For example, if a read value is ‘01,’ the arithmeticcomponent 404 increments the element that corresponds to the ‘01’ count.At block 1722, the histogram vector is provided to the example MUX 314via the example MUX 418 and the example latch 402 e and the example MUX314 outputs the histogram vector to the CPU 102 via the latch 322 b andthe CPU interface 202 (block 1722). In some examples, the histogramvector is additionally or alternatively, stored in the example mainstorage 214 via the ECC generator 412 and the arbitration manager 414.

FIGS. 18A and 18B illustrate an example flowchart representative ofexample machine readable instructions 1800 that may be executed by theexample L1 cache 110 of FIGS. 1-5 to perform an atomic compare and swapoperation, in conjunction with the above Sections 6 and/or 17. However,the flowchart may be described in conjunction with any atomic operationor a histogram operation. Although the instructions of FIGS. 18A and 18Bare described in conjunction with the L1 cache 110 of FIGS. 1-5, theinstructions may be described in conjunction with any type of storage inany type of cache. The instructions of FIGS. 18A and 18B are describedin conjunction with the main half of the L1 cache 110 (e.g., the maincache store queue 212, the main storage 214, etc.). However, theinstruction of FIGS. 18A and 18B can likewise be used in conjunctionwith the victim side of the L1 cache 110 (e.g., the victim cache storequeue 216, the victim storage 218, etc.).

At block 1802, the cache controller 220 and/or the example latch 402 bof the example main cache store queue 212 obtains an atomic compare andswap operation with a key from the example CPU 102. As described above,the atomic compare and swap compares the data at a memory address to akey and performs a write to the memory address with swap data if thepreviously stored data at the memory address matches the key. At block1804, the cache controller 220 interfaces with the example MESI RAM 300to determine the state of the memory address corresponding to the atomiccompare and swap operation. As described above in conjunction with FIGS.3A-3D, the MESI RAM 300 tracks the states of the memory addresses (e.g.,shared, modified, inactive, or exclusive). At block 1806, the cachecontroller 220 interfaces with the example MESI RAM 300 to determine ifthe state of the memory address is inactive (e.g., the memory addressedis not stored in the L1 cache 110) or is shared (e.g., stored in the L1cache 110 and stored in another higher level cache).

If the example cache controller 220 determines that the state of thememory address corresponding to the atomic compare and swap is inactiveof shared (block 1806: YES), the cache controller 220 causes the exampleL2 interface 228 to submit an atomic misinformation to higher levelcache with an exclusive state request (block 1808). As described abovein conjunction with FIG. 4A, if the memory address is stored in the L1cache 110 and is shared, writing to the data can cause problems if asecond core reads and/or writes the data at a different level of cache,because doing so will lead to inconsistent data for the same memoryaddress in different cache. Accordingly, the example L2 interface 228transmits the exclusive state request to let the higher level cache knowthat the L1 cache 110 will perform an operation on the cache for morethan one cycle so that different writes do not occur in different cachesto the same memory address.

At block 1810, the example cache controller 220 causes the example MESIRAM 300 to change the state of the corresponding memory address toexclusive. The MESI RAM 3400 may change the state after submitting therequest to higher level cache or after receiving a response from thehigher level cache. If the state of the memory address was inactive, thehigher level cache will return the data at the memory address, which maybe stored in the example main storage 214 and/or input to the exampleatomic compare component 406. At block 1812, the example cachecontroller 220 causes the example atomic compare component 406 to obtainthe data corresponding to the memory address (e.g., from the examplemain storage 214 and/or from the higher level cache).

If the example cache controller 220 determines that the state of thememory address does not correspond to the atomic compare and swap isinactive or shared (block 1806: NO), the example atomic comparecomponent 406 obtains the data corresponding to the memory address fromthe main storage 214 (block 1814). At block 1816, the cache controller220 causes the example atomic compare component 406 determines if theobtained data matches the key (e.g., from the atomic swap and compareoperation). If the example atomic compare component 406 determines thatthe obtained data does not match the key (block 1816: NO), the cachecontroller 220 causes the atomic compare component 406 to discard theswap data to be written from the atomic compare and swap (e.g., the datathat was to be stored if the obtained data matched the key) (block1818). In some examples, atomic compare component 406 outputs theobtained data to rewrite the obtained data back into the main storage214. If the example atomic compare component 406 determines that theobtained data matches the key (block 1816: YES), the cache controller220 causes the example atomic compare component 406 outputs the swapdata to be written to the memory address (e.g., from the atomic compareand swap operation) to the example MUX 410 (Block 1820).

At block 1822, the example cache controller 220 controls the MUX 410(e.g., via the select line) to ensure that the output of the atomiccompare component 406 is output to the example latch 402 d. Accordingly,the swapped data can be passed to the example ECC generation 412 togenerate an ECC code for the swapped data (block 1824).

At block 1826, the example ECC generation 412 outputs an ECC code forthe swapped data, the swapped data, and the memory address location tothe example to the example arbitration manager 414. At block 1828, thecache controller 220 causes the example arbitration manager 414 to storethe atomic output (e.g., the manipulated data) in the main storage 214at the memory address of the atomic operation.

FIG. 19 is an example flowchart representative of example machinereadable instructions 1900 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform in-flight data forwarding and invalidationof write instructions from the CPU 102, in conjunction with theabove-Section 7. Although the instructions of FIG. 19 are described inconjunction with the L1 cache 110 of FIGS. 1-5, the instructions may bedescribed in conjunction with any type of storage in any type of cache.

At block 1902, the cache controller 220 obtains a read-miss operationfrom the tag RAM accesses 204, 206. For example, the main cachecontroller 222 of the cache controller 220 obtains the read-missoperation when the CPU 102 issues a read operation that does not includea corresponding memory address in the main storage element 214 and/orthe victim storage element 214. The cache controller 220 determines avictim to evict from the main storage element 214 (block 1904). Forexample, the cache controller 220 creates a victim. The victimcorresponds to a memory address and a memory location (e.g., cache line)of the main storage element 214 to remove data from.

The cache controller 220 issues a read-invalidate operation to the storequeue 212 (block 1906). For example, the cache controller 220 sends anoperation to the read port 424 of the store queue in response toreceiving the memory address of the victim. The read port 424 obtains anaddress corresponding to victim (block 1908). For example, the cachecontroller 220 sends the victim address to the store queue 212 whenissuing a read-invalidate operation.

The data store 416 compares the address of the victim to addressesstored in the data store 416 (block 1910). For example, the data store416 maintains a log of the addresses associated with each value storedin any of the latches 402 a, 402 b, 402 c, 402 d, 402 e, and/or any ofthe merging circuits 403 a, 403 b, and/or 403 g. Additionally, the datastore 416 stores the victim address corresponding to the read-invalidateoperation. The data store 416 determines if any of the addresses in thedata store 416 match the address of the victim (block 1912). Forexample, the data store 416 determines if any of the latches 402 a-dinclude values and/or data corresponding to the victim address. In someexamples, the latches 402 a-d store outstanding write addresses. Theoutstanding write corresponds to a write operation has not beencompleted (e.g., the data of the write operation has not been fullywritten into the main storage element 214). In some examples, the storequeue 212 writes data to a location (e.g., a cache line) in the mainstorage element 214 that an allocation policy selected to be the victim.

If the data store 416 determines that any of the addresses in the datastore 416 match the address of the victim (e.g., block 1912 returns avalue YES), the priority multiplexer 418 forwards the data correspondingto the matching addresses to the MUX circuit 314 (block 1914). Forexample, the data store 416 sends the matching address to the prioritymultiplexer 418. The priority multiplexer 418 selects the data and/orthe values stored in the latches 402 a-d that store the victim address.The priority multiplexer 418 sends the selected data to the latch 402 eto be forwarded to the MUX circuit 314. The MUX circuit 314 sends thedata to the victim storage element 214 and/or the L2 cache 112.

The store queue 212 updates the valid tag in the appropriate latches(e.g., 402 a-d) to invalid (block 1916). For example, the latches thatstore data for the victim address change the valid tag to indicate thatthe data is invalid. In this manner, the store queue 212 willdiscontinue writing that data into the main storage element 214. Thus,the example read-invalidate operation 1900 corrects any errors thatwould occur if an outstanding write attempted to write data into a cacheline that no longer held the write operation address.

FIG. 20 is an example flowchart representative of example machinereadable instructions 2000 that may be executed by the example L1 cache110 of FIGS. 1-5 to determine whether an address is stored in a victimcache, such as the victim storage 218 of FIG. 2 as described above.Although the instructions of FIG. 20 are described in conjunction withthe L1 cache 110 of FIGS. 1-5, the instructions may be described inconjunction with any type of storage in any type of cache. Theinstructions of FIG. 20 are described in conjunction with the victimside of the L1 cache 110 (e.g., the victim cache store queue 216, thevictim storage 218, etc.). However, the instructions of FIG. 20 canlikewise be used in conjunction with the main half of the L1 cache 110(e.g., the main cache store queue 212, the main storage 214, etc.).

The machine readable instructions 2000 begin at block 2002, at which theL1 cache 110 receives read address(es) from interface(s). For example,the L1 cache 110 can receive ADP_ADDR_E2_DP0 from the scalar interface502 of the CPU 102 of FIG. 1, SNP_ADDR_E2_DP0 from the snoop interfaceof FIGS. 3 and/or 5, and/or ADP_ADDR_E2_DP1 from the vector interface502 of the CPU 102 as depicted in FIG. 8B.

At block 2004, the L1 cache 110 compares read address(es) to sets of amulti-bank victim cache tag (VCT) random access memory (RAM). Forexample, the first comparators 850 of FIG. 8B can compare a first readaddress of ADP_ADDR_E2_DP0 to respective addresses stored in the sets846 of FIG. 8B. In other examples, the second comparators 852 of FIG. 8Bcan compare a second read address of ADP_ADDR_E2_DP1 to respectiveaddresses stored in the sets 846.

At block 2006, the L1 cache 110 determines whether at least one of theread address(es) is mapped to one of the sets. For example, one of thefirst comparators 850 can assert a logic one in response to the readaddress matching the set 846 that the one of the first comparators 850is associated with. In other examples, the second comparators 852 cangenerate HIT_DP1 based on the comparisons. In other examples, the one ofthe first comparators 850 can generate a logic low in response to theread address not matching the set 846 that the one of the firstcomparators 850 corresponds to.

At block 2008, the L1 cache 110 identifies cache hit(s). For example,the first comparators 850 can generate HIT_DP0 based on the comparisons.In such examples, the first comparators 850 can identify a cache hit inresponse to at least one bit in the HIT_DP0 bit vector being a logic one(e.g., having a bit value of 1). In some such examples, the firstcomparators 850 can identify a cache miss in response to none of thebits in the HIT_DP0 bit vector being a logic one. In other examples, thesecond comparators 852 can generate HIT_DP1 based on the comparisons. Insuch examples, the second comparators 852 can identify a cache hit inresponse to at least one bit in the HIT_DP1 bit vector being a logicone. In some such examples, the second comparators 852 can identify acache miss in response to none of the bits in the HIT_DP1 bit vectorbeing a logic one.

At block 2010, the L1 cache 110 executes cache hit-miss conversionlogic. For example, the first address encoder logic circuit 854 caninvoke at least one of the first AND gate 864A, the third comparator870A, or the fourth comparator 872A of FIG. 8B to convert a cache hit toa cache miss or vice versa in response to example operating conditions.In other examples, the second address encoder logic circuit 856 caninvoke at least one of the second AND gate 864B, the fifth comparator870B, or the sixth comparator 872B of FIG. 8B to convert a cache hit toa cache miss or vice versa in response to example operating conditions.An example process that may be used to implement block 2010 is describedbelow in connection with FIG. 21.

At block 2012, the L1 cache 110 outputs cache hit address(es) based onthe cache hit-miss conversion logic. For example, the first addressencoder logic circuit 854 can output HIT_ADDR0 in response to executingcache hit-miss conversion logic. In other examples, the second addressencoder logic circuit 856 can output HIT_ADDR1 in response to executingcache hit-miss conversion logic.

At block 2014, the L1 cache 110 determines whether there additional readaddress(es) have been received. If, at block 2014, the L1 cache 110determines additional read address(es) have been received, controlreturns to block 2002 to receive the read address(es) from theinterface(s). If, at block 2014, the L1 cache 110 determines noadditional read address(es) have been received, the example machinereadable instructions 2000 of FIG. 20 conclude.

FIG. 21 is an example flowchart representative of example machinereadable instructions 2100 that may be executed by the example L1 cache110 of FIGS. 1-5 to execute cache hit-miss conversion logic as describedabove. The example machine readable instructions 2100 of FIG. 21 can beexecuted to implement block 2010 of FIG. 20. Although the instructionsof FIG. 21 are described in conjunction with the L1 cache 110 of FIGS.1-5, the instructions may be described in conjunction with any type ofstorage in any type of cache. The instructions of FIG. 21 are describedin conjunction with the victim side of the L1 cache 110 (e.g., thevictim cache store queue 216, the victim storage 218, etc.). However,the instructions of FIG. 21 can likewise be used in conjunction with themain half of the L1 cache 110 (e.g., the main cache store queue 212, themain storage 214, etc.).

The machine readable instructions 2100 of FIG. 21 begin at block 2102,at which the L1 cache 110 determines whether a new address from a firstinterface has been written to victim cache in a later pipeline stage.For example, the first decoder 860A can receive VTA_WR_SET0 at the E2pipeline stage, which can be representative of the scalar interface 502of FIG. 5 writing an address to the victim storage 218 at the E3pipeline stage.

If, at block 2102, the L1 cache 110 determines that a new address fromthe first interface is being written to the victim cache in a laterpipeline stage, control proceeds to block 2106 to compare the newaddress to the address of the cache hit. If, at block 2102, the L1 cache110 determines that a new address from the first interface is not beingwritten to the victim cache in a later pipeline stage, then, at block2104, the L1 cache 110 determines whether a new address from a secondinterface has been written to victim cache in a later pipeline stage.For example, the second decoder 860B can receive VTA_WR_SET1 at the E2pipeline stage, which can be representative of the scalar interface 502of FIG. 5 writing an address to the victim storage 218 at the E3pipeline stage.

If, at block 2104, the L1 cache 110 determines that a new address fromthe second interface is not being written to the victim cache in a laterpipeline stage, control returns to block 2012 of the example machinereadable instructions 2000 of FIG. 20 to output the cache hitaddress(es) based on the cache hit-miss conversion logic.

If, at block 2104, the L1 cache 110 determines that a new address fromthe second interface is being written to the victim cache in a laterpipeline stage, then at block 2106, the L1 cache 110 compares the newaddress to the address of the cache hit. For example, the first AND gate864A can assert a logic one in response to an address of VTAG_WR_SET0not matching an address of HIT_DP0. In other examples, the thirdcomparator 870A can compare an address of HIT_DP0 to an address beingwritten to the victim storage 218 by the scalar interface 502. In yetother examples, the fourth comparator 872A can compare an address ofHIT_DP0 to an address being written to the victim storage 218 by thevector interface 504.

In response to comparing the new address to address of the cache hit atblock 2106, control proceeds to block 2108 to determine whether theaddresses match. If, at block 2108, the L1 cache 110 determines that theaddresses do not match, control returns to block 2012 of the examplemachine readable instructions 2000 of FIG. 20 to output the cache hitaddress(es) based on the cache hit-miss conversion logic.

If, at block 2108, the L1 cache 110 determines that the addresses match,then, at block 2110, the L1 cache 110 determines whether a cache hit ora cache miss is identified. For example, the first AND gate 864A, thethird comparator 870A, and/or the fourth comparator 872A can determinethat there is a cache hit of the address of ADP_ADDR_E2_DP0 in thevictim storage 218 based on HIT_DP0 including at least one bit valueof 1. In other examples, the second AND gate 864B, the fifth comparator870B, and/or the sixth comparator 872B can determine that there is acache hit of the address of ADP_ADDR_E2_DP1 in the victim storage 218based on HIT_DP1 including at least one bit value of 1.

If, at block 2110, the L1 cache 110 determines that a cache hit isidentified, then, at block 2112, the L1 cache 110 converts the cache hitto a cache miss. For example, the first AND gate 864A can output a logiclow to convert a cache hit to a cache miss. In other examples, thesecond AND gate 864B can output a logic low to convert a cache hit to acache miss. In response to converting the cache hit to a cache miss atblock 2112, control returns to block 2012 of the example machinereadable instructions 2000 of FIG. 20 to output the cache hitaddress(es) based on the cache hit-miss conversion logic.

If, at block 2110, the L1 cache 110 determines that a cache miss isidentified, control proceeds to block 2114 to convert the cache miss toa cache hit in response to the new address matching a write from one(s)of the interface(s) allocating into victim cache. For example, the thirdcomparator 870A and/or the fourth comparator 872A can assert a logic oneto convert a cache miss to a cache hit in response to ADP_ADDR_E2_DP0matching an address of a write operation from either DP0 or DP1. Inother examples, the fifth comparator 870B and/or the sixth comparator872B can assert a logic one to convert a cache miss to a cache hit inresponse to ADP_ADDR_E2_DP1 matching an address of a write operationfrom either DP0 or DP1. In response to converting the cache miss to acache hit at block 2114, control returns to block 2012 of the examplemachine readable instructions 2000 of FIG. 20 to output the cache hitaddress(es) based on the cache hit-miss conversion logic.

FIG. 22 is an example flowchart representative of example machinereadable instructions 2200 that may be executed by the example L1 cache110 of FIGS. 1-5 to perform data allocation in the main storage 214, inconjunction with the above description. Although the instructions ofFIG. 22 are described in conjunction with the L1 cache 110 of FIGS. 1-5,the instructions may be described in conjunction with any type ofstorage in any type of cache.

The example main cache controller 222 (FIG. 2) obtains an instructionfrom the CPU interface 202 (FIG. 2). For example, the CPU interface 202provides an instruction to the cache controller 220, the cachecontroller 220 propagates the instruction to the main cache controller222.

The main cache controller 222 determines if the instruction is a readinstruction (block 2204). For example, the main cache controller 222analyzes the request in the instruction to determine if the main cachecontroller 222 is to read data from the main storage 214 and provide itto the CPU interface 202 or to perform a different task for the CPU 102.

If the main cache controller 222 determines the instruction is a readinstruction (e.g., block 2204 returns a value YES), the main cachecontroller 22 determines the address of the read instruction (block2206). For example, the main cache controller 222 determines where thedata is to be read from in the main storage 214. In some examples, themain tag RAM access 204 determines the address of the read instruction.

The main cache controller 222 determines if the address of the readinstruction matches an address in the tag RAMs 208, 210. For example,the cache controller 220 may obtain hit/miss results from the tag RAMaccess(es) 204, 206 and determine if the address is available in themain storage 214 and/or victim storage 218. The main cache controller222 determines the read instruction is a miss (e.g., block 2208 returnsa value NO), the main cache controller 223 identifies the cache lineassociated with the address (block 2210). For example, the main cachecontroller 222 is a direct mapped cache, and the address of the readinstruction can only be stored in one location (e.g., at one cache line)of the main storage 214.

The main cache controller 222 allocates data of the cache line to thevictim storage 218 (block 2212). For example, the main cache controller222 allocates data from the direct mapped cache line to the victimstorage 214. The main cache controller 222 allocates data regardless ofthe MESI state of that data. Such an allocation reduces latency of themain cache controller 222 and the overall L1 cache 110 by allocated anyline in the main storage 214 to the victim storage 218.

FIG. 23 is an example flowchart representative of example machinereadable instructions 2300 that may be executed by the example L1 cache110 of FIGS. 1-5 to facilitate a snoop request, in conjunction with theabove Section 10. At block 2302, the snoop address 502 (e.g., the snoopinterface) obtains the snoop request from a higher-level data cache(e.g., the L2 data cache 112). (Block 2302). In response, the snoopaddress 502 issues a read instruction to the tag RAM 210. (Block 2304).In examples disclosed herein, the read instruction is issued to the tagRAM 210 to identify whether the victim storage 218 includes the datarequested via the snoop address 502.

At block 2306, the comparison logic 306 c determines whether the readissued to the tag RAM 210 was a hit. (Block 2306). In the event thecomparison logic 306 c determines the read issued to the tag RAM 210 isnot a hit (e.g., the control of block 2306 returns a result of NO), thevictim storage 218 generates a snoop response indicating a missoccurred. (Block 2308). Additionally, the victim storage 218 transmitsthe snoop response back to the higher-level data cache (e.g., the L2data cache 112). (Block 2310).

Alternatively, in the event the comparison logic 306 determines the readissued to the tag RAM 210 is a hit (e.g., the control of block 2306returns a result of YES), the comparison logic 306 c determines thestate of the address associated with the read instruction in the MESIRAM 300. (Block 2312). At block 2312, the comparison logic 306 may alsostore the state of the address as identified responsive to the readinstruction in the MESI RAM 300.

At block 2314, the example address encoder 326 c generates an addressvalue for use by the victim storage 218 in obtaining the data. (Block2314). The address encoder 326 c encodes an address of the tag RAM 210to a form that is interpretable by the victim storage 218. For example,the tag RAM 210 may store 16-bit memory addresses while the victimstorage 218 stores 4-bit memory addresses corresponding to the 16-bitmemory addresses. Thus, the address encoder 326 may transform the 16-bitmemory address into a 4-bit memory address to locate and/or enter thecorresponding memory address in the victim storage 218.

At block 2316, the example response multiplexer 508 determines whether adata input is obtained from the victim cache store queue 216. (Block2316). In the event the response multiplexer 508 determines no data hasbeen input from the victim cache store queue 216 (e.g., the control ofblock 2316 returns a result of NO), the response multiplexer 508 outputsthe data identified based on the address provided by the address encoder326 c as the snoop response to the higher-level data cache (e.g., the L2data cache 112). (Block 2320).

Alternatively, in the event the response multiplexer 508 determines datahas been input from the victim cache store queue 216 (e.g., the controlof block 2316 returns a result of YES), the response multiplexer 508identifies the updated version of the data as the data to be sent in thesnoop response. (Block 2318). In response to the execution of thecontrol illustrated in block 2318, the response multiplexer 508 outputsthe data identified based on the address provided by the address encoder326 c as the snoop response to the higher-level data cache (e.g., the L2data cache 112). (Block 2320).

At block 2322, the snoop address component 506 (e.g., the snoopinterface) determines whether an additional snoop request is available.(Block 2322). In the event the snoop address component 506 (e.g., thesnoop interface) determines an additional snoop request is available(e.g., the control of block 2322 returns a result of YES), the process2300 returns to block 2302. Alternatively, in the event the snoopaddress component 506 (e.g., the snoop interface) determines anadditional snoop request is not available (e.g., the control of block2322 returns a result of NO), the process 2300 stops.

FIGS. 24, 25, 26, 27, 28, and 29A, 29B-1, and 29B-2 are exampleflowcharts representative of example machine readable instructions thatmay be executed by the example L1 cache 110 of FIGS. 1-5 to performeviction of data in the victim storage 218, in conjunction with theabove Section 11. Although the instructions of FIGS. 24, 25, 26, 27, 28,and 29A, 29B-1, and 29B-2 are described in conjunction with the L1 cache110 of FIGS. 1-5, the instructions may be described in conjunction withany type of storage in any type of cache.

FIG. 24 illustrates an example first operation 2400 of the replacementpolicy component 308 (FIGS. 3 and 5) when the first and second datapaths (DP0 and DP1) include valid transactions. FIG. 25 illustrates anexample second operation 2500 of the replacement policy component 308when the first and second data paths (DP0 and DP1) include validtransactions. FIG. 26 illustrates an example third operations 2600 ofthe replacement policy component 308 when the first and second datapaths (DP0 and DP1) include valid transactions. FIG. 27 illustrates anexample valid-invalid operation 2700 of the replacement policy component308 when the first data path is a valid transaction and the second datapath is an invalid transaction. FIG. 28 illustrates an exampleinvalid-valid operation 2800 of the replacement policy component 308when the first data path is an invalid transaction and the second datapath is a valid transaction. FIG. 29A, FIG. 29B-1, and FIG. 29B-2illustrate an incrementing operation 2900 of the replacement policycomponent 308 when a data path is allocating data to the victim storage.

Turning to FIG. 24, the example scalar interface 502 and the examplevector interface 504 determine if the first and second data paths arevalid transactions (block 2402). For example, the scalar interface 502determines if the first data path DP0 is accessing (e.g., requesting aread or write operation) the victim storage 218 and the vector interface504 determines if the second data path DP1 is accessing the victimstorage 218. When the interfaces 502, 504 determine the first and seconddata paths are valid transactions (e.g., block 2402 returns a valueYES), the replacement policy component 308 obtains results from thehit-miss comparison logic 306 a, 306 b (block 2404). For example, thereplacement policy component 308 obtains results indicating whether thefirst data path access and the second data path access have matchingaddresses in the tag RAM 210 or do not.

The example replacement policy component 308 determines if the resultsindicate that both of the transactions of the first data path and thesecond data path are hits (block 2406). When the replacement policycomponent 308 determines DP0 and DP1 are both hits (e.g., block 2406returns a value yes), the least recently used value Y remains constant(block 2408). For example, since neither the first data path nor thesecond data path needs to evict data, the LRU value does not need tochange.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2410). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2410 returns a value YES) then control returns to block2402. If the replacement policy component 308 does not obtain hit-missresults corresponding to different transactions (e.g., accesses) thanthe previous accesses (e.g., block 2410 returns a value NO) then thefirst operation 2400 ends.

When the replacement policy component 308 determines the results do notindicate that both of the transactions of the first data path and thesecond data path are hits (e.g., block 2406 returns a value NO), thereplacement policy component 308 determines if the results indicate thatboth of the transactions of the first data path and the second data pathare misses (block 2412). For example, the replacement policy component308 determines if both results from the first hit-miss comparison logic306 a and the second hit-miss comparison logic 306 b indicate neither ofthe accesses matched the addresses in the tag RAM 210.

If DP0 and DP1 missed (e.g., block 2412 returns a value YES), then thereplacement policy component 308 points the first data path to the LRUway (Y) (block 2414). The replacement policy component 308 points thesecond data path to the next LRU way (Y+1) (block 2416). For example,the victim storage 218 includes n number of ways, each way has alocation (e.g., slot 1, slot 2, slot n), each way is mapped to anaddress, and each way includes data. The replacement policy component308 initializes a value Y to be equal to the least recently used way inthe victim cache. For example, the LRU way is slot 2, thus Y is equal toslot 2. When the replacement policy component 308 points the first datapath to the LRU way (block 2414), the replacement policy component 308is assigning the location of Y in the victim storage 218 to DP0 foreviction. Similarly, when the replacement policy component 308 pointsthe second data path to the next LRU way (block 2416), the replacementpolicy component 308 is assigning the location of Y+1 in the victimstorage 218 to DP1 for eviction.

The example replacement policy component 308 provides the pointer valuesto the example multiplexers 330 a, 330 b (block 2418). For example, thereplacement policy component 308 provides a location (Y) of the way thatis to be evicted by DP0 from the victim storage 218 to the multiplexer330 a and a location (Y+1) of the way that is to be evicted by DP1 tothe multiplexer 330 b. In some examples, the selecting input of themultiplexer 330 a and 330 b selects the replacement policy componentinput, the address read 332 a and 332 b reads the input of thereplacement policy component 308 and evicts the ways indicated bylocation Y and location Y+1.

The example replacement policy component 308 increments Y by two (block2420). For example, the replacement policy component 308 assigns Y to alocation in the victim storage 218 that is two slots away from thecurrent value of Y (e.g., if Y=slot 1, then Y=slot 3 afterincrementing). In this manner, during the next clock cycle, thereplacement policy component 308 is provided with an updated andappropriate Y value. Alternatively and/or additionally, the replacementpolicy component 308 increments indicators for the first and second datapaths by two.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2422). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2422 returns a value YES) then control returns to block2402. If the replacement policy component 308 does not obtain hit-missresults corresponding to different transactions (e.g., accesses) thanthe previous accesses (e.g., block 2420 returns a value NO) then thefirst operation 2400 ends.

Turning to FIG. 25, when the replacement policy component 308 determinesthe results indicate that the first data path and the second data pathare not both misses (e.g., block 2412 returns a value NO), the examplereplacement policy component 308 determines if the results indicate thatthe first data path is a hit and the second data path is a miss (block2502).

If the example replacement policy component 308 determines that thefirst data path is a hit and the second data path is a miss (e.g., block2502 returns a value YES), then the replacement policy componentdetermines the location in the victim storage 218 of the hit way (DP0Way) (block 2504). For example, the replacement policy component 308analyzes the address of DP0 and identifies the location in the victimstorage 218 that includes that address. In some examples, thereplacement policy component 308 may include an updated list of theelements in the victim storage 218. In other examples, the replacementpolicy component 308 retrieves and/or obtains information from the tagRAM 210 regarding the locations of the addresses stored in the victimstorage 218.

The example replacement policy component 308 determines if the hit way(DP0 Hit Way) matches the location of the next LRU value (Y+1) (block2506). For example, the replacement policy component 308 may compare thelocation of the hit way containing the address of DP0 to the locationvalue assigned to Y+1. If the replacement policy component 308determines that the locations are match (e.g., block 2506 returns avalue YES), then the replacement policy component 308 switches theassignment of the next LRU value and the LRU value (block 2508). Forexample, the second data path DP1 pointer is to be assigned to the LRUvalue (e.g., location Y) instead of the next LRU value (e.g., locationY+1). The replacement policy component 308 switches the assignment toavoid the second data path DP1 evicting the DP0 Hit Way. In someexamples, the replacement policy component 308 decrements an indicatorto indicate the LRU way of the victim storage 214 to be evicted by thesecond data path DP1.

The replacement policy component 308 points the second data path to theLRU way (Y) (block 2510). For example, the replacement policy component308 assigns the value of Y (e.g., the location of the LRU way) to thesecond data path DP1 for eviction.

The example replacement policy component 308 provides the pointer valuesto the multiplexer(s) 330 a, 330 b (block 2512). For example, thereplacement policy component 308 provides a location (Y) of the way thatis to be evicted by DP1 from the victim storage 218 to the multiplexer330 b. In some examples, when the hit way does not match the location ofthe next LRU value (e.g., block 2506 returns a value NO), thereplacement policy component 308 provides the pointer value Y+1 and thelocation of the hit way to the multiplexer(s) 330 a, 330 b. For example,the original assignment of the next LRU value to the second data pathDP1 remains the same.

The example replacement policy component 308 increments Y based oneviction (block 2514). For example, if the assignments of LRU values todata paths were switched (e.g., DP1 pointer points to the LRU value Y),then the replacement policy component 308 increments Y by one.Otherwise, the replacement policy component 308 increments Y by two. Inthis manner, during the next clock cycle, the replacement policycomponent 308 is provided with an updated Y value and Y+1 value.Alternatively and/or additionally, the replacement policy component 308increments indicators for the first and second data paths based oneviction.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2516). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2516 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2516 returns a valueNO) then the second operation 2500 ends.

Turning to FIG. 26, when the replacement policy component 308 determinesthe results indicate that the first data path is not a hit and thesecond data path is not a miss (e.g., block 2602 returns a value NO),the example replacement policy component 308 determines that the resultsindicate that the first data path is a miss and the second data path isa hit (block 2602).

The example replacement policy component 308 determines the location inthe victim storage 218 of the hit way (DP1 Way) (block 2604). Forexample, the replacement policy component 308 analyzes the address ofDP1 and identifies the location in the victim storage 218 that includesthat address.

The example replacement policy component 308 determines if the hit way(DP1 Way) matches the location of the LRU value (Y) (block 2606). Forexample, the replacement policy component 308 may compare the locationof the hit way containing the address of DP1 to the location valueassigned to Y. If the replacement policy component 308 determines thatthe locations match (e.g., block 2606 returns a value YES), then thereplacement policy component 308 switches the assignment of the LRUvalue and the next LRU value (block 2608). For example, first data pathDP0 pointer is to be assigned to the next LRU value (e.g., location Y+1)instead of the LRU value (e.g., location Y). The replacement policycomponent 308 switches the assignment to avoid the first data path DP0evicting the DP1 Hit Way. In some examples, the replacement policycomponent 308 increments an indicator to indicate the next LRU way inthe victim storage 214 to be evicted by the first data path DP0.

The replacement policy component 308 points the first data path to thenext LRU value (Y+1) (block 2610). For example, the replacement policycomponent 308 assigns the value of Y+1 (e.g., the location of the nextLRU way) to the first data path DP0 for eviction.

The example replacement policy component 308 provides the pointer valuesto the multiplexer(s) 330 a, 330 b (block 2612). For example, thereplacement policy component 308 provides a location (Y+1) of the waythat is to be evicted, by DP0, from the victim storage 218 to themultiplexer 330 a. In some examples, when the hit way does not match thelocation of the LRU value (e.g., block 2506 returns a value NO), thereplacement policy component 308 provides the pointer value Y and thelocation of the hit way to the multiplexer(s) 330 a, 330 b. For example,the original assignment of the LRU value to the first data path DP0remains the same.

The example replacement policy component 308 increments Y based oneviction (block 2614). For example, if the assignments of LRU values todata paths were switched (e.g., DP0 pointer points to the next LRU valueY+1), then the replacement policy component 308 increments Y by two.Otherwise, the replacement policy component 308 increments Y by one. Inthis manner, during the next clock cycle, the replacement policycomponent 308 is provided with an updated Y value. Alternatively and/oradditionally, the replacement policy component 308 increments indicatorsfor the first and second data paths based on eviction.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2616). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2616 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2616 returns a valueNO) then the third operation 2600 ends.

Turning to FIG. 27, when the example scalar interface 502 and theexample vector interface 504 determine the first and second data pathsare not valid transactions (e.g., block 2402 returns a value NO), theexample scalar interface 502 and the example vector interface 504determine if the first data path is valid and the second data path isinvalid (block 2702). For example, the scalar interface 502 determinesif the first data path DP0 is accessing (e.g., requesting a read orwrite operation) the victim storage 218 and the vector interface 504determines if the second data path DP1 is not attempting to access thevictim storage 218.

When the interfaces 502, 504 determine the first data path is a validtransaction and the second data path is an invalid transaction (e.g.,block 2702 returns a value YES), the replacement policy component 308obtains results from the hit-miss comparison logic 306 a (block 2704).For example, the replacement policy component 308 obtains a resultindicating whether the first data path access has a matching addressesin the tag RAM 210 or does not have a matching address in the tag RAM210. The example replacement policy component 308 determines if theresults indicate that first data path is a hit (block 2706). If thereplacement policy component 308 determines the address of the firstdata path DP0 hits an address in the tag RAM 210 (e.g., block 2706returns a value YES), the least recently used value Y remains constant(block 2708). For example, since the first data path does not need toevict data, the LRU value does not need to change.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2710). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2710 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2710 returns a valueNO) then the first operation 2700 ends.

When the example replacement policy component 308 determines that theresults do not indicate that first data path is a hit (e.g., block 2706returns a value NO), then the first data path is a miss (block 2712).

The example replacement policy component 308 points the first data pathto the LRU Way (Y) (block 2714). For example, the replacement policycomponent 308 assigns the location of Y in the victim storage 218 to DP0for eviction.

The example replacement policy component 308 provides the pointer valueto the first multiplexer 330 a (block 2716). For example, thereplacement policy component 308 provides the location the LRU way tothe first multiplexer 330 a for eviction of that way.

The example replacement policy component 308 increments Y (block 2718).For example, the replacement policy component 308 updates the LRU way tothe next location (e.g., Y+1) in the victim storage 218. Alternativelyand/or additionally, the replacement policy component 308 incrementsindicators for the first and second data paths.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2720). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2720 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2720 returns a valueNO) then the first operation 2700 ends.

Turning to FIG. 28, when the example scalar interface 502 and theexample vector interface 504 determine the first data path is not avalid transaction and the second data path is a valid transactions(e.g., block 2702 returns a value NO), the example scalar interface 502and the example vector interface 504 determine the first data path isinvalid and the second data path is valid (block 2802). For example, thescalar interface 502 determines that the first data path DP0 is notaccessing (e.g., requesting a read or write operation) the victimstorage 218 and the vector interface 504 determines if the second datapath DP1 is accessing the victim storage 218.

The replacement policy component 308 obtains results from the hit-misscomparison logic 306 b (block 2804). For example, the replacement policycomponent 308 obtains a result indicating whether the second data pathaccess has a matching addresses in the tag RAM 210 or does not have amatching address in the tag RAM 210.

The example replacement policy component 308 determines if the resultsindicate that second data path is a hit (block 2806). If the replacementpolicy component 308 determines the address of the second data path DP1hits an address in the tag RAM 210 (e.g., block 2806 returns a valueYES), the least recently used value Y remains constant (block 2808). Forexample, since the second data path does not need to evict data, the LRUvalue does not need to change.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2810). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2810 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2810 returns a valueNO) then the first operation 2700 ends.

When the example replacement policy component 308 determines that theresults do not indicate that second data path is a hit (e.g., block 2806returns a value NO), then the second data path is a miss (block 2812).

The example replacement policy component 308 points the second data pathto the LRU Way (Y) (block 2814). For example, the replacement policycomponent 308 assigns the location of Y in the victim storage 218 to DP1for eviction.

The example replacement policy component 308 provides the pointer valueto the second multiplexer 330 b (block 2816). For example, thereplacement policy component 308 provides the location the LRU way tothe second multiplexer 330 b for eviction of that way.

The example replacement policy component 308 increments Y (block 2818).For example, the replacement policy component 308 updates the LRU way tothe next location (e.g., Y+1) in the victim storage 218. Alternativelyand/or additionally, the replacement policy component 308 incrementsindicators for the first and second data paths.

The example replacement policy component 308 determines if a transactionon a new clock cycle has been received (block 2820). For example, if thereplacement policy component 308 obtains hit-miss results correspondingto different transactions (e.g., accesses) than the previous accesses(e.g., block 2820 returns a value YES) then control returns to block2402 of FIG. 24. If the replacement policy component 308 does not obtainhit-miss results corresponding to different transactions (e.g.,accesses) than the previous accesses (e.g., block 2820 returns a valueNO) then the first operation 2800 ends.

The machine readable instructions 2400, 2500, 2600, 2700, and 2800correspond to the first table 602 of FIG. 6.

FIG. 29A, FIG. 29B-1, and FIG. 29B-2 are example flowchartsrepresentative of example machine readable instructions 2900 that may beexecuted by the L1 cache 110 of FIGS. 1-5 to perform LRU incrementing inthe victim storage 214 based on the allocation status of a data path, inconjunction with the above description.

The machine readable instructions 2900 begin at block 2902, at which thereplacement policy component 308 initializes the first data pathallocate pointer to equal location Y. For example, the replacementpolicy component 308 assigns a portion of the victim storage 218 notrecently used by the CPU 102, having location Y, to the LRU value. Insuch an example, when the first data path DP0 is to allocate, the victimstorage 218 evicts data from the LRU value (e.g., location Y). Thereplacement policy component 308 initializes the second data pathallocate pointer to equal location Y+1 (block 2904). For example, thereplacement policy component 308 assigns a portion of the victim storage218 not recently used by the CPU 102, having location Y+1, to the nextLRU value. In such an example, when the second data path DP1 is toallocate, the victim storage 218 evicts data from the next LRU value(e.g., location Y+1).

The replacement policy component 308 determines the first and seconddata paths are valid transactions (block 2906). For example, the CPU 102provided instructions on both data paths.

The replacement policy component 308 determines if the first data pathDP0 is a hit in the victim storage 218 and the second data path DP1 isto allocate (block 2908). If the first data path DP0 hits the victimstorage 218 and the second data path DP1 is allocating to the victimstorage 218 (e.g., block 2908 returns a value YES), the replacementpolicy component 308 determines the location in the victim storage 218of the of the hit location (DP0 Hit Way) (block 2910). For example, thereplacement policy component 308 identifies where the address of the DP0is in the victim storage 218.

The replacement policy component 308 determines if the hit location isequal to the location of the second data path allocate pointer (Y+1)(block 2912). For example, the replacement policy component 308determines if the address of DP0 matches the location of Y+1. If thelocations do match (e.g., block 2912 returns a value YES), thereplacement policy component 308 updates the second data path allocatepointer to equal location Y (block 2914). For example, the replacementpolicy component 308 switches the assignment of the second data pathallocate pointer from Y+1 to Y to avoid evicting data requested on theDP0 instruction.

The cache controller 220 performs the first transaction and the secondtransaction (block 2916). For example, the cache controller 220reads/writes data of DP0 at location Y+1 and evicts data from location Yin the victim storage 218.

The replacement policy component 308 increments the first data pathallocate pointer by one (block 2918). For example, since the cachecontroller 220 evicted data from location Y and not Y+1, the replacementpolicy component 308 only needs to update the LRU value to the next LRUvalue (Y+1).

If the hit location and the second data path allocate pointer do notmatch (e.g., block 2912 returns a value NO), the cache controller 220performs the first transaction and the second transaction (block 2920).For example, the replacement policy component 308 determines that Y+1includes data that is available to evict and thus, the second data pathallocate pointer can evict data from that location while the first datapath DP0 reads/writes data from the hit location.

The replacement policy component 308 increments the first data pathallocate pointer by two (block 2922). For example, since the cachecontroller 220 evicts data from the location Y+1, the replacement policycomponent 308 updates the LRU value Y to a location after the evictedlocation (e.g., LRU value=Y+2 and the next LRU value=Y+3).

If the replacement policy component 308 determines the condition ofblock 2908 is not true (e.g., block 2908 returns a value NO), thereplacement policy component 308 determines if the first data path is toallocate and the second data path hits (block 2924). For example, thereplacement policy component 308 determines if the second data path hitsa location in the victim storage 218 and if the main storage 214 isallocating data on the first data path DP0.

If the replacement policy component 308 determines the first data pathis to allocate and the second data path is a hit (e.g., block 2924returns a value YES), the replacement policy component 308 determinesthe location in the victim storage 218 of the hit location (DP2 Way)(block 2926). For example, the replacement policy component 308determines where the second data path is reading/writing data from inthe victim storage 218.

Turning to FIG. 29B-1, the replacement policy component 308 determinesif the hit location is equal to the location Y (block 2928). Forexample, the replacement policy component 308 determines if the firstdata path allocate pointer points to the same location storing the hitdata.

If the replacement policy component 308 determines the locations match(e.g., block 2928 returns a value YES), the replacement policy component308 updates the first data path allocate pointer to equal location Y+1(block 2930). For example, the replacement policy component 308 switchesthe assignments of the LRU value and the next LRU value to avoid thefirst data path evicting the hit data from the victim storage 218.

The cache controller 220 performs the first transaction and the secondtransaction (block 2932). For example, the cache controller 220reads/writes data from the location Y and evicts data of the locationY+1. The replacement policy component 308 increments the pointer Y bytwo locations (block 2934). For example, the replacement policycomponent 308 updates the LRU location to a location after the mostrecently evicted location (e.g., in this example, the most recentlyevicted location is Y+1, therefore the LRU value is incremented by twoto equal Y+2).

If the replacement policy component 308 determines the hit location doesnot match the location of the originally assigned first data pathpointer (Y) (e.g., block 2928 returns a value NO), the cache controller220 performs the first transaction and the second transaction (block2936). For example, the replacement policy component 308 determines thatY includes data that is available to evict and thus, the first data pathallocate pointer can evict data from that location while the second datapath DP1 reads/writes data from the hit location.

The replacement policy component 308 increments the first data pathallocate pointer by one location (block 2938). For example, since thecache controller 220 evicts data from the location Y, the replacementpolicy component 308 updates the LRU value Y to a location after theevicted location. In this manner, the replacement policy component 308includes an updated LRU value and an updated next LRU value during thenext clock cycle.

If the condition of block 2924 of FIG. 29A is not true (e.g., block 2924returns a value NO when the first data path is not to allocate when thesecond data path is to hit), then control moves to FIG. 29B-2 where thereplacement policy component 308 determines both data paths are toallocate (block 2940). For example, if two read-misses occur, the mainstorage 214 allocates two lines from the main storage 214 to the victimstorage 218.

In this manner, the cache controller 220 performs the first transactionand the second transaction (block 2942). For example, the cachecontroller 220 evicts data from the LRU location (Y) utilizing the firstdata path DP0 and evicts data from the next LRU location (Y+1) utilizingthe second data path DP1.

The replacement policy component 308 increments the first data pathallocate pointer by two (block 2944). For example, the replacementpolicy component 308 increments the location Y by two locations sincedata was evicted from Y+1. In some examples, when the LRU value isincremented by a value, the next LRU value is incremented simultaneouslyby the same value. Therefore, the first data path allocate pointer andthe second data path allocate pointer always point to an updated andaccurate eviction location.

The machine readable instructions 2900 correspond to the second table604 of FIG. 6.

FIG. 30 is an example flowchart representative of example machinereadable instructions 3000 that may be executed by the example L1 cache110 of FIGS. 1-5 to execute arbitration logic to perform a read, modify,or write operation as described above. Although the instructions of FIG.30 are described in conjunction with the L1 cache 110 of FIGS. 1-5, theinstructions may be described in conjunction with any type of storage inany type of cache. The instructions of FIG. 30 are described inconjunction with the main half of the L1 cache 110 (e.g., the main cachestore queue 212, the main storage 214, etc.). However, the instructionsof FIG. 30 can likewise be used in conjunction with the victim side ofthe L1 cache 110 (e.g., the victim cache store queue 216, the victimstorage 218, etc.).

The machine readable instructions 3000 of FIG. 30 begin at block 3002,at which the L1 cache 110 obtains store instruction(s) from interface(s)coupled to hardware. For example, the address processing components 302a-c of FIGS. 3A-3D can obtain the first store instruction 1018 from thescalar interface, the second store instruction 1020 from the memoryinterface, and/or the third store instruction 1022 from the vectorinterface. Alternatively, the address processing components 302 a-c ofFIGS. 3A-3D can obtain the first store instruction 1018 b from thescalar interface, the second store instruction 1020 b from the memoryinterface, and/or the third store instruction 1022 b from the vectorinterface of FIG. 10B.

At block 3004, the L1 cache 110 generates transaction data based on thestore instruction(s). For example, the address processing components 302a-c and/or the bank processing logic 303 of FIGS. 3A-3D can generate thefirst transaction data, the second transaction data, and/or the thirdtransaction data of FIG. 10A. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 of FIGS. 3A-3Dcan generate the first transaction data, the second transaction data,and/or the third transaction data of FIG. 10B. An example process thatmay be used to implement block 3004 is described below in connectionwith FIG. 31.

At block 3006, the L1 cache 110 determines whether read operation(s)is/are identified based on the transaction data. For example, theaddress processing components 302 a-c can determine that at least one ofthe first store instruction 1018, the second store instruction 1020, orthe third store instruction 1022 includes a request to have a readoperation serviced (e.g., a value of RD_BANK_REQ[i] is indicative of aread request, a logic high signal for RD_BANK_REQ[i], etc.). In suchexamples, the read operation request can be determined based on the R/Wdata included in the store instructions 1018, 1020, 1022. Alternatively,the address processing components 302 a-c can determine that at leastone of the first store instruction 1018 b, the second store instruction1020 b, or the third store instruction 1022 b includes a request to havea read operation serviced (e.g., a value of RD_BANK_REQ[i] is indicativeof a read request, a logic high signal for RD_BANK_REQ[i], etc.). Insuch examples, the read operation request can be determined based on theR/W data included in the store instructions 1018 b, 1020 b, 1022 b ofFIG. 10B.

If, at block 3006, the L1 cache 110 determines that there are no readoperations identified based on the transaction data, control proceeds toblock 3014 to invoke second arbitration logic to write the data to thestore queue. If, at block 3006, the L1 cache 110 determines that thereis at least one read operation identified based on the transaction data,then, at block 3008, the L1 cache 110 invokes first arbitration logic tolocate data for the read operation(s) in at least one of a store queueor storage. For example, the address processing components 302 a-c caninvoke the first arbitration logic 1008 to locate data for the readoperation(s) in at least one of the main cache store queue 212 or themain storage 214. Alternatively, the address processing components 302a-c can invoke the first arbitration logic 1008 b to locate data for theread operation(s) in at least one of the victim cache store queue 216 orthe victim storage 218. An example process that may be executed toimplement block 3008 is described below in connection with FIG. 20.

At block 3010, the L1 cache 110 identifies the most recent version ofthe located data. For example, the L1 cache 110 can compare a firstversion of the requested data from the main cache store queue 212 to asecond version of the requested data from the main storage 214 anddetermine that the first version is more recent than the second versionbased on the comparison. Alternatively, the L1 cache 110 can compare afirst version of the requested data from the victim cache store queue216 to a second version of the requested data from the victim storage218 and determine that the first version is more recent than the secondversion based on the comparison.

At block 3012, the L1 cache 110 delivers the most recent version of thelocated data to store queue to execute a modify operation on the readand write data. For example, the main cache store queue 212 can deliverand/or otherwise transmit the first version of the requested data to themain cache store queue 212 to execute a modify operation on therequested data and the data to be written. Alternatively, the victimcache store queue 216 can deliver and/or otherwise transmit the firstversion of the requested data to the victim cache store queue 216 toexecute a modify operation on the requested data and the data to bewritten.

At block 3014, the L1 cache 110 invokes the second arbitration logic towrite the data to the store queue or the storage. For example, the firstarbitration logic 1008 can transmit an instruction to the secondarbitration logic 1010 to write the WDATA or portion(s) thereof to atleast one of the main cache store queue 212 or the main storage 214.Alternatively, the first arbitration logic 1008 b can transmit aninstruction to the second arbitration logic 1010 b to write the WDATA orportion(s) thereof to at least one of the victim cache store queue 216or the victim storage 218 of FIG. 10B. In response to invoking thesecond arbitration logic to write the data to the store queue or thestorage at block 3014, the example machine readable instructions 3000 ofFIG. 30 conclude.

FIG. 31 is an example flowchart representative of example machinereadable instructions 3100 that may be executed by the example L1 cache110 of FIGS. 1-5 to generate transaction data based on storeinstruction(s) as described above. The flowchart of FIG. 31 can be anexample implementation of the machine readable instructions 3004 of FIG.30. Although the instructions of FIG. 31 are described in conjunctionwith the L1 cache 110 of FIGS. 1-5, the instructions may be described inconjunction with any type of storage in any type of cache. Theinstructions of FIG. 31 are described in conjunction with the main halfof the L1 cache 110 (e.g., the main cache store queue 212, the mainstorage 214, etc.). However, the instructions of FIG. 31 can likewise beused in conjunction with the victim side of the L1 cache 110 (e.g., thevictim cache store queue 216, the victim storage 218, etc.).

The machine readable instructions 3100 begin at block 3102, at which theL1 cache 110 extracts write data from the store instruction(s) based ona number of data storage banks. For example, the address processingcomponents 302 a-c and/or the bank processing logic 303 of FIGS. 3A-3Dcan extract the WDATA from the store instructions 1018, 1020, 1022 basedon a quantity of data banks that the main cache store queue 212 and/orthe main storage 214 are broken up into. In such examples, in responseto the main cache store queue 212 having 16 data banks, the cache linecan be 64 bits and, thus, WDATA can be extracted in 64 bit chunks.Alternatively, the address processing components 302 a-c and/or the bankprocessing logic 303 of FIGS. 3A-3D can extract the WDATA from the storeinstructions 1018 b, 1020 b, 1022 b of FIG. 10B based on a quantity ofdata banks that the victim cache store queue 216 and/or the victimstorage 218 are broken up into. In such examples, in response to thevictim cache store queue 216 having 16 data banks, the cache line can be64 bits and, thus, WDATA can be extracted in 64 bit chunks.

At block 3104, the L1 cache 110 rotates the write data to generaterotated write data. For example, the address processing components 302a-c can rotate the CPU-Write Data of the first store instruction 902 ofFIGS. 3A-3D to generate the rotated data 904 of FIG. 9.

At block 3106, the L1 cache 110 determines byte enable data based on thestore instruction(s). For example, the address processing components 302a-c and/or the bank processing logic 303 can determine the BYTEN/BANK[i]data of FIG. 10A based on the BYTEN data included in the storeinstructions 1018, 1020, 1022. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 can determinethe BYTEN/BANK[i] data of FIG. 10B based on the BYTEN data included inthe store instructions 1018 b, 1020 b, 1022 b.

At block 3108, the L1 cache 110 determines a data access operation datasize based on the store instruction(s). For example, the addressprocessing components 302 a-c and/or the bank processing logic 303 candetermine the data size of data to be read, written, and/or modifiedbased on the SIZE data included in the store instructions 1018, 1020,1022. Alternatively, the address processing components 302 a-c and/orthe bank processing logic 303 can determine the data size of data to beread, written, and/or modified based on the SIZE data included in thestore instructions 1018 b, 1020 b, 1022 b.

At block 3110, the L1 cache 110 determines a data storage address basedon the store instruction(s). For example, the address processingcomponents 302 a-c and/or the bank processing logic 303 can determinethe MS_ADDR[i] of a corresponding bank of the main cache store queue 212and/or the STQ_ADDR[i] address of a corresponding bank of the mainstorage 214 based on the ADDR data included in the store instructions1018, 1020, 1022. Alternatively, the address processing components 302a-c and/or the bank processing logic 303 can determine the VS_ADDR[i] ofa corresponding bank of the victim cache store queue 216 and/or theSTQ_V_ADDR[i] address of a corresponding bank of the victim storage 218based on the ADDR data included in the store instructions 1018 b, 1020b, 1022 b.

At block 3112, the L1 cache 110 maps the data access operation data sizeand the data storage address to a first quantity of data banks to readfrom. For example, the address processing components 302 a-c and/or thebank processing logic 303 can map the data access operation size and thedata storage address to zero or more banks of the main cache store queue212, zero or more banks of the main storage 214, etc., to generateRD_BANK_REQ[i] of FIG. 10A. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 can map the dataaccess operation size and the data storage address to zero or more banksof the victim cache store queue 216, zero or more banks of the victimstorage 218, etc., to generate RD_BANK_REQ[i] of FIG. 10B.

At block 3114, the L1 cache 110 maps the data access operation data sizeand the data storage address to a second quantity of data banks to writeto. For example, the address processing components 302 a-c and/or thebank processing logic 303 can map the data access operation size and thedata storage address to zero or more banks of the main cache store queue212, zero or more banks of the main storage 214, etc., to generateWR_BANK_REQ[i] of FIG. 10A. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 can map the dataaccess operation size and the data storage address to zero or more banksof the victim cache store queue 216, zero or more banks of the victimstorage 218, etc., to generate WR_BANK_REQ[i] of FIG. 10B.

At block 3116, the L1 cache 110 generates transaction data based on atleast one of the first quantity, the second quantity, the byte enabledata, or the write data. For example, the address processing components302 a-c and/or the bank processing logic 303 can generate the firsttransaction data (TRANSACTION_DP0[i]), the second transaction data(TRANSACTION_DMA[i]), and the third transaction data(TRANSACTION_DP1[i]) of FIG. 10A. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 can generate thefirst transaction data (TRANSACTION_DP0[i]), the second transaction data(TRANSACTION_DMA[i]), and the third transaction data(TRANSACTION_DP1[i]) of FIG. 10B. In response to generating thetransaction data based on at least one of the first quantity, the secondquantity, the byte enable data, or the write data at block 3116, controlreturns to block 3006 of the machine readable instructions 3000 of FIG.30 to determine whether read operation(s) is/are identified based on thetransaction data.

FIG. 32 is an example flowchart representative of example machinereadable instructions 3200 that may be executed by the example L1 cache110 of FIGS. 1-5 to invoke first arbitration logic to locate data forread operation(s) in at least one of a store queue or storage asdescribed above. The flowchart of FIG. 32 can be an exampleimplementation of the machine readable instructions 3008 of FIG. 30.Although the instructions of FIG. 32 are described in conjunction withthe L1 cache 110 of FIGS. 1-5, the instructions may be described inconjunction with any type of storage in any type of cache. Theinstructions of FIG. 32 are described in conjunction with the main halfof the L1 cache 110 (e.g., the main cache store queue 212, the mainstorage 214, etc.). However, the instructions of FIG. 32 can likewise beused in conjunction with the victim side of the L1 cache 110 (e.g., thevictim cache store queue 216, the victim storage 218, etc.).

The machine readable instructions 3200 begin at block 3202, at which theL1 cache 110 selects a data storage bank of interest to process. Forexample, the address processing components 302 a-c and/or the bankprocessing logic 303 of FIGS. 3A-3D can select the first bank 1002 ofFIG. 10A to process. Alternatively, the address processing components302 a-c and/or the bank processing logic 303 of FIGS. 3A-3D can selectthe first bank 1002 b of FIG. 10B to process.

At block 3204, the L1 cache 110 compares selected data storage bank todata storage banks included in read bank request(s) from interface(s).For example, the first arbitration logic 1008 can compare the bank(s)identified in respective one(s) of RD_BANK_REQ[i] from the scalarinterface, the memory interface, and the vector interface to the firstbank 1002 (e.g., STQ[0], MS[i], etc.). Alternatively, the firstarbitration logic 1008 b can compare the bank(s) identified inrespective one(s) of RD_BANK_REQ[i] from the scalar interface, thememory interface, and the vector interface to the first bank 1002 b(e.g., STQ_V[0], VS[i], etc.).

At block 3206, the L1 cache 110 determines whether at least oneinterface requests access to the selected data storage. If, at block3206, the L1 cache 110 determines that none of the interfaces requestaccess to the selected data bank, control proceeds to block 3208 todetermine that the selected data storage bank is not used for readoperation(s). In response to determining that the selected data storagebank is not used for read operation(s) at block 3208, control returns toblock 3202 to select another data storage bank of interest to process.

If, at block 3206, the L1 cache 110 determines that at least oneinterface requests access to the selected data bank, control proceeds toblock 3210 to determine whether more than one interface requests accessto the selected data storage bank. If, at block 3210, the L1 cache 110determines that only one interface requests access to the selected datastorage bank, control proceeds to block 3212 to invoke first arbitrationlogic to assign the selected data storage bank to the requestinginterface. In response to invoking the first arbitration logic to assignthe selected data storage bank to the requesting interface at block3212, control returns to block 3202 to select another data storage bankof interest to process.

If, at block 3210, the L1 cache 110 determines that more than oneinterface requests access to the selected data storage bank, controlproceeds to block 3214 to invoke the first arbitration logic to assignthe selected data storage bank to the requesting interface requiring aread operation. For example, the first arbitration logic 1008 can assignthe first bank 1002 to the one of the interfaces requiring a readoperation as read operations are prioritized over write operations.Alternatively, the first arbitration logic 1008 b can assign the firstbank 1002 b to the one of the interfaces requiring a read operation asread operations are prioritized over write operations.

At block 3216, the L1 cache 110 invokes the first arbitration logic toinform second arbitration logic that the requesting interface requiringa write operation is not assigned the selected data storage bank. Forexample, if scalar data path is requesting a write operation and a readoperation and the scalar data path is not assigned the first data bank1002 for the read operation, the first arbitration logic 1008 caninstruct the second arbitration logic 1010 to not assign the scalar datapath the first data bank 1002 and, thus, stall and/or otherwise preventexecution of the write operation since the corresponding read operationis not to be completed during the clock cycle. Alternatively, if scalardata path is requesting a write operation and a read operation and thescalar data path is not assigned the first data bank 1002 b for the readoperation, the first arbitration logic 1008 can instruct the secondarbitration logic 1010 b to not assign the scalar data path the firstdata bank 1002 b and, thus, stall and/or otherwise prevent execution ofthe write operation since the corresponding read operation is not to becompleted during the clock cycle.

At block 3218, the L1 cache 110 determines whether to select anotherdata storage bank of interest to process. For example, the addressprocessing components 302 a-c and/or the bank processing logic 303 candetermine to select a second bank of the main cache store queue 212 andthe main storage 214 to process. Alternatively, the address processingcomponents 302 a-c and/or the bank processing logic 303 can determine toselect a second bank of the victim cache store queue 216 and the victimstorage 218 to process. If, at block 3218, the L1 cache 110 determinesto select another data storage bank of interest to process, controlreturns to block 3202 to select another data storage bank of interest toprocess. If, at block 3218, the L1 cache 110 determines not to selectanother data storage bank of interest to process, control returns toblock 3010 of the machine readable instructions 3000 of FIG. 30 toidentify the most recent version of the located data.

FIG. 33 is an example flowchart representative of example machinereadable instructions 3300 that may be executed by the example L1 cache110 of FIGS. 1-5 to facilitate a read-modify-write operation in thevictim storage 216, in conjunction with the above Section 13. In FIG.33, the victim cache store queue 216 obtains a write instructiontransmitted by the CPU 102 (e.g., transmitted through the cachecontroller 220) indicating byte(s) of a word, or an entire word, to bere-written. (Block 3302). In some examples disclosed herein, the writeport 1126 may obtain the write instruction transmitted by the CPU 102.

At block 3304, the victim cache store queue 216 transmits the value ofthe portion of the word to be rewritten to the latch 1102 b. (Block3304). In some examples, the latch 1102 b transmits the value of theportion of the word to be rewritten to the latch 1102 c.

At block 3306, the victim cache store queue 216 stores the address valueassociated with the location of the portion of the word to be rewrittenin the pending store address data store 1116. (Block 3306).Additionally, the tag ram 210 transmits a read instruction (e.g., a readrequest) of the entire currently stored word to the victim storage 218.(Block 3308). At block 3310, the victim cache store queue 216 determineswhether there has been a subsequent clock cycle of the CPU 102, or thecache controller 220. (Block 3310). In some examples disclosed herein,the latch 1102 c determines whether there has been a subsequent clockcycle of the CPU 102, or the cache controller 220. In response todetermining that there has not been a subsequent clock cycle of the CPU102, or the cache controller 220, (e.g., the control of block 3310returns a result of NO), the process waits.

Alternatively, in response to determining that there has been asubsequent cycle of the CPU 102, or the cache controller 220, (e.g., thecontrol of block 3310 returns a result of YES), the read-modify-writemerge component 1108 obtains the value of the portion of the word (e.g.,the byte) stored in the latch 1102 c. (Block 3312). Additionally, theread-modify-write merge component 1108 obtains the entire currentlystored word transmitted by the ECC logic 312. (Block 3314). In thismanner, the read-modify-write merge 1108 identifies the address of thebyte in the currently stored word to be updated. Once theread-modify-write merge component 1108 identifies and/or otherwiseobtains (a) the value (e.g., byte value, bit value, etc.) of the portionof the currently stored word to be updated from the latch 1102 c and the(b) currently stored word from the ECC logic 312, the read-modify-writemerge component 1108 writes (e.g., replaces) the portion of thecurrently stored word with the value of the portion of the currentlystored word obtained from the latch 1102 c. (Block 3316). For example,the read-modify-write merge component 1108 writes the value of theportion of the word to an address value corresponding to the portion ofthe word in the word.

At block 3318, the victim cache store queue 216 generates errordetection code based on the word, the error detection code to be storedwith the word. (Block 3318). In some examples disclosed herein the ECCgenerator 1112 generates error detection code based on the word, theerror detection code to be stored with the word.

The control of block 3318 may be performed in response to an additionalsubsequent clock cycle of the CPU 102, or the cache controller 220.

In response, the victim cache store queue 216 determines whether anadditional write instruction is obtained. (Block 3322). the event thevictim cache store queue 216 determines another write instruction isobtained (e.g., the control of block 3322 returns a result of YES), theprocess returns to block 3302. Alternatively, in the event the victimcache store queue 216 determines another write instruction is notobtained (e.g., the control of block 3322 returns a result of NO), theprocess 3300 may wait until a threshold timeout period occurs, thusending the process 3300.

FIG. 34 is a block diagram of an example processor platform 3400structured to execute the instructions of FIGS. 12-33 to implement theL1 cache 110 of FIGS. 1-5 and 10-11. The processor platform 1000 can be,for example, a server, a personal computer, a workstation, aself-learning machine (e.g., a neural network), a mobile device (e.g., acell phone, a smart phone, a tablet such as an iPad™), a personaldigital assistant (PDA), an Internet appliance, a gaming console, or anyother type of computing device.

The processor platform 3400 of the illustrated example includes aprocessor 3412. The processor 3412 of the illustrated example ishardware. For example, the processor 3412 can be implemented by one ormore integrated circuits, logic circuits, microprocessors, GPUs, DSPs,or controllers from any desired family or manufacturer. The hardwareprocessor may be a semiconductor based (e.g., silicon based) device. Inthis example, the processor implements any element of the example L1cache 110 as shown in FIGS. 1-5 and 10-11.

The processor 3412 of the illustrated example includes a local memory3413 (e.g., a cache). The processor 3412 of the illustrated example isin communication with a main memory including a volatile memory 3414 anda non-volatile memory 3416 via a bus 3418. The volatile memory 3414 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random AccessMemory (RDRAM®) and/or any other type of random access memory device.The non-volatile memory 3416 may be implemented by flash memory and/orany other desired type of memory device. Access to the main memory 3414,3416 is controlled by a memory controller.

The processor platform 3400 of the illustrated example also includes aninterface circuit 3420. The interface circuit 3420 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface.

In the illustrated example, one or more input devices 3422 are connectedto the interface circuit 3420. The input device(s) 3422 permit(s) a userto enter data and/or commands into the processor 3412. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 3424 are also connected to the interfacecircuit 3420 of the illustrated example. The output devices 3424 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 3420 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 3420 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 3426. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 3400 of the illustrated example also includes oneor more mass storage devices 3428 for storing software and/or data.Examples of such mass storage devices 3428 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives.

The machine executable instructions 3432 of FIGS. 12-33 may be stored inthe mass storage device 3428, in the volatile memory 3414, in thenon-volatile memory 3416, and/or on a removable non-transitory computerreadable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus and articles of manufacture have been disclosed to facilitateatomic compare and swap in cache for a coherent level 1 data cachesystem. The disclosed methods, apparatus and articles of manufactureimprove the efficiency of using a computing device by reducing a datacache to reduce latency of a computing system and improving computersystem efficiency to reduce stress on a computer core. The disclosedmethods, apparatus and articles of manufacture are accordingly directedto one or more improvement(s) in the functioning of a computer.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

The following claims are hereby incorporated into this DetailedDescription by this reference, with each claim standing on its own as aseparate embodiment of the present disclosure.

What is claimed is:
 1. A circuit device comprising: a first cache memoryassociated with a cache hierarchy and configured to store a first set ofdata; a state memory configured to store a state of each unit of data ofthe first set of data; a cache controller coupled to the first cachememory and the state memory and configured to couple to a second cachememory associated with the cache hierarchy, wherein the cache controlleris configured to: receive a compare-and-swap operation that specifies amemory address; and based on the compare-and-swap operation: determinewhether a second set of data associated with the memory address isstored in the first cache memory; based on the second set of data notbeing in the first set of data stored in the first cache memory, providea request for the second set of data from the second cache memory; andbased on the second set of data being in the first set of data stored inthe first cache memory: determine, based on the state memory, a stateassociated with the second set of data; and based on the stateassociated with the second set of data being a shared state, provide therequest for the second set of data from the second cache memory.
 2. Thecircuit device of claim 1, wherein the cache controller is configuredto, based on the second set of data being in the first set of datastored in the first cache memory and the state associated with thesecond set of data being a modified state or an exclusive state, use thefirst set of data stored in the first cache memory to perform thecompare-and-swap operation.
 3. The circuit device of claim 1, whereinthe request for the second set of data from the second cache memoryspecifies an exclusive state for the second set of data.
 4. The circuitdevice of claim 1, wherein the cache controller is configured to set thestate associated with the second set of data in the state memory to anexclusive state based on providing the request to the second cachememory.
 5. The circuit device of claim 1, wherein the cache controlleris configured to set the state associated with the second set of data inthe state memory to an exclusive state based on receiving the second setof data from the second cache memory.
 6. The circuit device of claim 1,wherein: the compare-and-swap operation further specifies a third set ofdata and a fourth set of data; and the cache controller is configuredto: compare the second set of data to the third set of data; and basedon the second set of data matching the third set of data, write thefourth set of data to the first cache memory.
 7. The circuit device ofclaim 6, wherein the cache controller is configured to, based on thesecond set of data matching the third set of data, overwrite the secondset of data with the fourth set of data.
 8. The circuit device of claim7, wherein the cache controller is configured to, overwrite the secondset of data with the fourth set of data after storage after beinggranted an exclusive state for the second set of data from the secondcache memory.
 9. The circuit device of claim 1, wherein the first cachememory is a level-one (L1) cache memory and the second cache memory is alevel-two (L2) cache memory.
 10. The circuit device of claim 9, whereinthe first cache memory includes at least one of a L1 main cache memoryor a L1 victim cache memory.
 11. The circuit device of claim 1 furthercomprising a processor coupled to the cache controller and configured toprovide the compare-and-swap operation.
 12. The circuit device of claim1 further comprising a tag random access memory coupled to the cachecontroller, wherein the cache controller is configured to determinewhether the set of data associated with the memory address is stored inthe first cache memory based on the tag random access memory.
 13. Amethod comprising: receiving, by a cache controller, a compare-and-swapoperation that specifies a memory address; determining, by the cachecontroller, whether a set of data associated with the memory address isstored in a first cache memory; based on the set of data being stored inthe first cache memory, determining a coherency state of the set of datain the first cache memory; and based on the coherency state of the setof data being a shared state, requesting, by the cache controller, theset of data from a second cache memory.
 14. The method of claim 13,wherein the requesting of the set of data from the second cache memoryincludes requesting the set of data in an exclusive state.
 15. Themethod of claim 13 further comprising setting the coherency state of theset of data in the first cache memory to an exclusive state based on therequesting of the set of data from the second cache memory.
 16. Themethod of claim 13 further comprising setting the coherency state of theset of data in the first cache memory to an exclusive state based onreceiving the set of data from the second cache memory.
 17. The methodof claim 13, wherein: the set of data is a first set of data; thecompare-and-swap operation further specifies a second set of data and athird set of data; and the method further comprises: comparing the firstset of data to the second set of data; and based on the first set ofdata matching the second set of data, writing the third set of data tothe first cache memory.
 18. The method of claim 17, wherein the writingof the third set of data overwrites the first set of data in the firstcache memory.
 19. The method of claim 18, wherein the writing of thethird set of data performed after being granted an exclusive state forthe first set of data from the second cache memory.
 20. The method ofclaim 13, wherein the first cache memory is a level-one (L1) cachememory and the second cache memory is a level-two (L2) cache memory.